Intervertebral implants, systems, and methods of use

ABSTRACT

An intervertebral implant frame that is configured to engage a spacer can include a pair of arms that extend longitudinally from a support member such that the arms engage the spacer. The spacer can be made from bone graft, and include a first spacer body made of cortical bone, and a second spacer body made of cancellous bone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No. 14/520,690 filed on Oct. 22, 2014, the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein.

BACKGROUND

Implants for spinal fusion typically include a spacer to allow for growth of bone between adjacent vertebral bodies while restoring and maintaining intervertebral space height that is defined between the vertebral bodies. In some cases, a plate is used to provide stability during healing so as to allow the patient to quickly resume an active lifestyle. The profile of the plate, which is placed on the anterior aspect of the vertebral bodies, however, can lead to dysphasia or patient discomfort which has precipitated the development of what's known as “zero-profile” devices. One example of a conventional minimal-profile intervertebral implant is insertable substantially entirely into the intervertebral space so as to not substantially extend beyond the footprint of the vertebral bodies that define the intervertebral space.

Other intervertebral implants have been utilized that include a frame shaped in a manner so as to interface with a spacer made from PEEK. Such spacer bodies typically are customized to have complimentary features to the frame so that the spacer bodies may be affixed to the frame. Such frames may not be desirable for spacer bodies made from allograft, however, because allograft spacer bodies may vary in shape, may not include the complimentary features needed to be affixed to the frame, and may degrade or resorb overtime.

SUMMARY

In accordance with one embodiment, an intervertebral implant is configured to be inserted into an intervertebral space. The intervertebral implant can include a spacer and a frame. The spacer, in turn, can include a cortical spacer body comprising a cortical bone graft material, and a cancellous spacer body comprising a cancellous bone graft material. The cancellous spacer body can be disposed proximal with respect to at least a portion of the cortical spacer body. The frame can include a support member disposed proximal with respect to the cancellous spacer body and configured to extend along a portion of the cancellous spacer body, such that the cancellous spacer body is disposed between the support member and the at least a portion of the cortical spacer body. The frame can further include first and second opposed arms that extend from the support member and are configured to engage the cortical spacer body.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of embodiments of the application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the methods, implants and systems of the present application, there is shown in the drawings preferred embodiments. It should be understood, however, that the application is not limited to the precise methods, implants, and systems shown. In the drawings:

FIG. 1A is a perspective view of an intervertebral implant assembly that is implanted in an intervertebral space defined by a superior vertebral body and an inferior vertebral body, the intervertebral implant assembly including an intervertebral implant and at least a pair of fixation elements that attach the intervertebral implant to the superior vertebral body and the inferior vertebral body, respectively;

FIG. 1B is a side elevation view of the intervertebral implant assembly as shown in FIG. 1A, the intervertebral space defining an anterior-posterior midline;

FIG. 1C is a top plan view of the inferior vertebral body shown in FIG. 1B;

FIG. 2A is a perspective view of the intervertebral implant illustrated in FIGS. 1A and 1B, the intervertebral implant having an intervertebral implant frame and a spacer retained by the intervertebral implant frame;

FIG. 2B is a top plan view of the intervertebral implant shown in FIG. 2A;

FIG. 2C is a top plan view of an intervertebral implant similar to FIG. 2B, but showing the frame secured to the spacer in accordance with one embodiment;

FIG. 2D is a top plan view of an intervertebral implant similar to FIG. 2C, but showing the frame secured to the spacer in accordance with another embodiment;

FIG. 2E is a top plan view of an intervertebral implant similar to FIG. 2D, but showing the frame secured to the spacer in accordance with yet another embodiment;

FIG. 2F is a top plan view of an intervertebral implant similar to FIG. 2B, but showing the frame secured to the spacer in accordance with still another embodiment;

FIG. 3A is a perspective view of the intervertebral implant frame shown in FIG. 2, the intervertebral implant frame having a support member, a first arm extending from the support member, and a second arm extending from the support member, the first and second arms configured to elastically flex away from each other;

FIG. 3B is a front elevation view of the intervertebral implant frame shown in FIG. 3A;

FIG. 3C is a top plan view of the intervertebral implant frame shown in FIG. 3A;

FIG. 3D is a side elevation view of the intervertebral implant frame shown in FIG. 3A;

FIG. 3E is a cross-sectional view of the intervertebral implant frame shown in FIG. 3D through the line 3E-3E;

FIG. 3F is another perspective view of the intervertebral implant frame shown in FIG. 3A;

FIG. 4A is a perspective view of one embodiment of the fixation elements that is configured to affix the intervertebral implant shown in FIG. 2 to a vertebral body as illustrated in FIGS. 1A and 1B;

FIG. 4B is a side elevation view of the of the fixation element shown in FIG. 4A;

FIG. 5A is a perspective view of an intervertebral implant system constructed in accordance with an embodiment, the system including an actuation instrument configured as an expansion instrument that includes an actuation grip illustrated as an expansion grip that is configured to actuate the frame shown in FIG. 3A from a first configuration to a second configuration whereby the frame is configured to receive a spacer, for example of the type shown in FIG. 2A;

FIG. 5B is a perspective view of the expansion instrument shown in FIG. 5A, the expansion instrument including a first expansion arm and a second expansion arm coupled to the first expansion arm at a first pivot, each expansion arm having a handle portion and a gripping portion that combine to define a handle of the expansion instrument and the expansion grip illustrated in FIG. 5A;

FIG. 5C is a top plan view of the expansion instrument shown in FIG. 5B;

FIG. 5D is a detailed view of one of the gripping portions of the expansion instrument shown in FIG. 5B;

FIG. 5E is an enlarged top plan view of the expansion grip shown in FIG. 5B, coupled to the first and second arms of the frame shown in FIG. 3A, showing the expansion instrument actuated from a first position to a second position, whereby the expansion grip applies an expansion force to the first and second arms of the frame when the expansion instrument is in the second position, the expansion force biasing the first and second arms of the frame to flex away from each other;

FIG. 5F is a perspective view of an expansion instrument in accordance with another embodiment, shown coupled to the intervertebral implant frame;

FIG. 5G is a perspective view of a first member of the expansion instrument illustrated in FIG. 5F

FIG. 5H is a perspective view of a second member of the expansion instrument illustrated in FIG. 5F

FIG. 5I is a sectional end elevation view of the expansion instrument illustrated in FIG. 5F, shown coupled to the intervertebral implant frame;

FIG. 5J is a sectional plan view of the expansion instrument illustrated in FIG. 5F, shown coupled to the intervertebral implant frame;

FIG. 6A is a perspective view of a spacer of the type illustrated in FIG. 2A, including a cortical spacer body and a cancellous spacer body, and a force transfer member that extends through the cancellous spacer body and at least into the cortical spacer body;

FIG. 6B is another perspective view of the spacer illustrated in FIG. 6A;

FIG. 6C is a top plan view of the spacer illustrated in FIG. 6A;

FIG. 6D is a sectional side elevation view of the spacer illustrated in FIG. 6A;

FIG. 6E is a top plan view of the cancellous spacer body illustrated in FIG. 6A;

FIG. 6F is a perspective view of the cancellous spacer body illustrated in FIG. 6E;

FIG. 6G is another perspective view of the cancellous spacer body illustrated in FIG. 6E;

FIG. 6H is a perspective view of the cortical spacer body illustrated in FIG. 6A;

FIG. 6I is a top plan view of the cortical spacer body illustrated in FIG. 6H;

FIG. 6J is a perspective view of the force transfer member illustrated in FIG. 6A;

FIG. 6K is a sectional side elevation view of the spacer as illustrated in FIG. 6A, but including parallel top and bottom surfaces;

FIG. 6L is a sectional side elevation view of the spacer illustrated in FIG. 6A, but showing an aperture extending through the cortical spacer body and including angled (e.g. lordotic) top and bottom surfaces;

FIG. 6M is a sectional side elevation view of the spacer illustrated in FIG. 6L, but including parallel top and bottom surfaces;

FIG. 7A is a perspective view of a spacer as illustrated in FIG. 6A, but including surface geometry in accordance with an alternative embodiment;

FIG. 7B is a perspective view of a spacer as illustrated in FIG. 7A, but including surface geometry in accordance with an another embodiment;

FIG. 7C is a perspective view of a spacer as illustrated in FIG. 6A, but including surface geometry in accordance with an another embodiment;

FIG. 7D is a perspective view of a spacer as illustrated in FIG. 7C, but including surface geometry in accordance with an another embodiment;

FIG. 7E is a perspective view of a spacer as illustrated in FIG. 7D, but including surface geometry in accordance with an another embodiment;

FIG. 7F is a perspective view of a spacer as illustrated in FIG. 7E, but including surface geometry in accordance with an another embodiment;

FIG. 8A is a top plan view of the spacer as illustrated in FIG. 6A, but including engagement members constructed in accordance with an alternative embodiment;

FIG. 8B is a sectional side elevation view of the spacer illustrated in FIG. 8A;

FIG. 9A is a top plan view of the spacer as illustrated in FIG. 6A, but including engagement members constructed in accordance with an another alternative embodiment;

FIG. 9B is a sectional side elevation view of the spacer illustrated in FIG. 9A;

FIG. 10A is a top plan view of the spacer as illustrated in FIG. 6A, but constructed in accordance with yet another alternative embodiment;

FIG. 10B is a sectional side elevation view of the spacer illustrated in FIG. 10A;

FIG. 11A is an exploded perspective view of a spacer similar to the spacer illustrated in FIG. 6A, but constructed in accordance with an alternative embodiment;

FIG. 11B is a top plan view of an intervertebral implant including a frame attached to the spacer illustrated in FIG. 11A;

FIG. 11C is a to plan view of an intervertebral implant including a frame attached to a spacer constructed in accordance with an alternative embodiment;

FIG. 11D is a perspective view of the spacer illustrated in FIG. 11C;

FIG. 12A is a perspective view of an intervertebral spacer constructed in accordance with an alternative embodiment, including grooves configured to engage the intervertebral implant frame illustrated in FIG. 3A;

FIG. 12B is another perspective view of the intervertebral spacer as illustrated in FIG. 12A, but including smooth opposed lateral surfaces so as to engage an intervertebral implant frame in accordance with an alternative embodiment;

FIG. 12C is an exploded perspective view of the intervertebral spacer illustrated in FIG. 12B;

FIG. 12D is another exploded perspective view of the intervertebral spacer illustrated in FIG. 12B;

FIG. 12E is a schematic front elevation view of the intervertebral spacer of FIGS. 12A and 12B, showing apertures created by fixation elements that extend through the frame and into the corresponding vertebral body; and

FIG. 12F is a schematic front elevation view showing apertures created by fixation elements that extend through the frame and into the corresponding vertebral body, the apertures configured in accordance with an alternative embodiment.

DETAILED DESCRIPTION

Referring to FIGS. 1A and 1B, a superior vertebral body 10 a defines a first or superior vertebral surface 14 a of an intervertebral space 18, and an adjacent second or inferior vertebral body 10 b defines an inferior vertebral surface 14 b of the intervertebral space 18. Thus, the intervertebral space 18 is disposed between or otherwise defined by the vertebral bodies 10 a and 10 b. The vertebral bodies 10 a and 10 b can be anatomically adjacent vertebral bodies, or can remain after a portion of bone has been removed. The intervertebral space 18 can be disposed anywhere along the spine as desired, including at the lumbar, thoracic, and cervical regions of the spine. As illustrated, the intervertebral space 18 is illustrated after a discectomy, whereby the disc material has been removed or at least partially removed to prepare the intervertebral space 18 to receive an intervertebral implant 22. As shown, the intervertebral implant 22 can be affixed to the superior and inferior vertebral bodies 10 a and 10 b with respective fixation elements 62. The intervertebral implant 22 and the fixation elements 62 together define an intervertebral implant assembly 24.

Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, “left”, “lower” and “upper” designate directions in the drawings to which reference is made. The words “inner” or “distal” and “outer” or “proximal” refer to directions toward and away from, respectively, the geometric center of the implant and related parts thereof. The words, “anterior”, “posterior”, “superior,” “inferior,” “medial,” “lateral,” and related words and/or phrases are used to designate various positions and orientations in the human body to which reference is made and are not meant to be limiting. The terminology includes the above-listed words, derivatives thereof and words of similar import.

The intervertebral implant 22 is described herein as extending horizontally along a longitudinal direction “L” and lateral direction “A”, and vertically along a transverse direction “T”. Unless otherwise specified herein, the terms “lateral,” “longitudinal,” and “transverse” are used to describe the orthogonal directional components of various components. It should be appreciated that while the longitudinal and lateral directions are illustrated as extending along a horizontal plane, and that the transverse direction is illustrated as extending along a vertical plane, the planes that encompass the various directions may differ during use. For instance, when the intervertebral implant 22 is implanted into the intervertebral space 18 along an insertion direction I, the transverse direction T extends vertically generally along the superior-inferior (or caudal-cranial) direction, while the horizontal plane defined by the longitudinal direction L and lateral direction A lies generally in the anatomical plane defined by the anterior-posterior direction, and the medial-lateral direction, respectively. Thus, the lateral direction A can define the medial-lateral direction when the implant 22 is implanted in the intervertebral space. The longitudinal direction L can define the anterior-posterior direction when the implant 22 is implanted in the intervertebral space. Accordingly, the directional terms “vertical” and “horizontal” are used to describe the intervertebral implant 22 and its components as illustrated merely for the purposes of clarity and illustration.

As shown in FIGS. 1B and 1C, the vertebral surfaces 14 a and 14 b of the vertebral bodies 10 a and 10 b can define a geometrical centroid M that is generally located at an anterior-posterior midpoint between an anterior end and a posterior end of the surfaces 14 a and 14 b. As shown in FIG. 1B, the intervertebral implant 22 is configured to be disposed or otherwise implanted in the intervertebral space 18 such that a portion of the intervertebral implant 22 is located on a posterior side of a medial lateral plane that intersects the centroid M, and a portion of the intervertebral implant 22 is located on an anterior side of the medial lateral plane that intersects the centroid M.

In reference to FIGS. 1A, 1B, 2A and 2B, the intervertebral implant 22 includes an intervertebral implant frame 26 and an intervertebral spacer 30 that is retained by the frame 26. In one example, the spacer 30 is configured to be received by the frame 26. Thus, it can be said that the frame 26 is configured to receive the spacer 30. The intervertebral implant 22, defines a proximal end P and a distal end D. The distal end D is spaced from the proximal end P in a distal direction, which is along the longitudinal direction L. When the intervertebral implant 22 is implanted in an intervertebral space, the proximal end P can define an anterior end, and the distal end D can define a posterior end spaced from the anterior end in an anterior-posterior direction. The intervertebral implant 22 is configured to be inserted into the intervertebral space in an insertion direction. In one example, the insertion direction can be in the distal direction, such that the distal direction can be referred to as an insertion direction into the intervertebral space. It should be appreciated, of course, the intervertebral implant 22 can be inserted into the intervertebral space along any suitable direction as desired, for instance in the lateral direction A. Alternatively, the intervertebral implant 22 can be inserted in an oblique direction that includes both the distal direction and the lateral direction A. Thus, the insertion direction can be in at least the distal direction, which can include the distal direction and the oblique direction. Further, it should be appreciated that the intervertebral implant 22 is configured to be inserted into the thoracic region, and the lumbar region of the spine. Further, it should be appreciated that the intervertebral implant 22 is configured to be inserted into the thoracic region, and the lumbar region of the spine. Conversely, the proximal end P is spaced from the distal end D in a proximal direction that is opposite the distal direction, and also is along the longitudinal direction L. The frame 26 may be made from any biocompatible material, such as TAN alloy, or PEEK. The spacer 30 can be composed of a bone graft such as allograft bone, autograft bone or xenograft bone. It should be appreciated that the spacer 30 can further include ceramics, polymers, metals, and biomaterials. In particular, the spacer 30 can include a cortical spacer body 410 made of cortical bone graft material, and a cancellous spacer body 412 made of cancellous bone graft material. By using a spacer 30 composed of bone graft, surface area for fusion can be maximized with respect to synthetic spacers. Additionally, the bone graft promotes bony in-growth of the respective vertebral bodies into the spacer 30, and increased probability and speed of sound fusion between the spacer and the respective vertebral bodies. The frame 26 is configured to be attached to various bone graft spacer footprint geometries, which may or may not conform to the internal footprint of the frame 26. It should be further appreciated that the insertion direction can be in the distal direction, and that the distal direction can be oriented in a lateral approach into the intervertebral space, an anterior-posterior approach into the intervertebral space, or an oblique approach into the intervertebral space. The oblique approach can be oblique to both the anterior-posterior approach and the lateral approach.

As shown in FIGS. 3A-3E the frame 26 includes a support member 34, a first arm 38 that extends from the support member 34, and a second arm 42 that extends from the support member 34. In the illustrated embodiment, the first and second arms 38 and 42 are flexible arms that extend from opposed ends of the support member 34 such that the support member 34, the first arm 38, and the second arm 42 together create a three wall structure that retains and secures the spacer 30 to the frame 26.

As shown in FIGS. 3A-3C, the support member 34 includes a body 46 that defines an inner surface 50, an outer surface 54, and at least one, such as two or such as four, fixation element receiving apertures 58 that extend through the body 46 from the outer surface 54 to the inner surface 50. Each fixation element receiving aperture 58 is configured to receive a respective fixation element, such as fixation element 62 shown in FIGS. 4A and 4B. While the fixation elements 62 are illustrated as screws, it should be appreciated that the fixation elements 62 may also be nails or any other fixation element configured to attach the intervertebral implant 22 to the first and second vertebral bodies 10 a and 10 b. As shown, the support member 34 can further include at least one tab 64 such as a plurality of tabs 64 that extend from the body 46 generally along the transverse direction T. For instance, the support member 34 can include three tabs 64. The tabs 64 may be disposed at an anterior side of the vertebral bodies and prevent over-insertion of the frame 26 into the intervertebral space 18. In the illustrated embodiment, the support member 34 includes a pair of superior tabs 64 that extend in an upward or superior direction from the body 35, and an inferior tab 64 that extends in a downward or inferior direction from the body 35. Each of the tabs 64 can be configured to sit flush or slightly proud of an anterior surface of the vertebral bodies depending on the patient's spinal anatomy and/or site preparation. It should be appreciated, however, that the support member 34 can include other configurations for the tabs 64. For example, the support member 34 can include a single superior tab 64 and a pair of inferior tabs 64. Alternatively still, as described in more detail below with respect to FIG. 3F, the support member can include a pair of superior tabs and a pair of inferior tabs.

As shown in FIG. 3B, two of the fixation element receiving apertures 58 are inner apertures 66 that extend through the body 46 at a downward angle relative to the insertion direction I, and two of the fixation element receiving apertures 58 are outer apertures 70 that extend through the body 46 at an upward angle relative to the insertion direction I. The inner apertures 66 are configured to receive respective fixation elements, such as fixation element 62 shown in FIGS. 4A and 4B, to thereby attach the intervertebral implant 22 to the inferior vertebral body 10 b. Similarly, the outer apertures 70 are configured to receive respective fixation elements 62 to thereby attach the intervertebral implant 22 to the superior vertebral body 10 a. It should be appreciated, however, that the inner apertures 66 can extend through the body 46 at an upwards angle and the outer apertures 70 can extend through the body 46 at a downwards angle, as desired. Moreover, it should be appreciated that the support member 34 can define any number of fixation element receiving apertures 58 as desired. It should be appreciated that the fixation element receiving apertures 58 can be configured as boreholes sized to accommodate the fixation elements 62, or can be configured as recesses or a partial boreholes in order to accommodate the fixation elements 62.

As shown in FIG. 3B, the apertures 58 each define internal threads 78. The internal threads 78 are configured to engage external threads 80 defined by a head 82 of the respective fixation element 62 (see FIGS. 4A-4B) that is received within the apertures 58, such that the internal threads 78 mate with the external threads 80. It should be appreciated, however, that the apertures 58 can be void of threads as desired. The orientation of the apertures 58 may be configured such that the fixation elements that are received by the apertures 58 may have an insertion variance of +/−5 degrees and do not allow toggling or settling. Once fully received, the fixation elements may lock to the frame 26 to thereby increase the surgeon's reassurance of good screw trajectories and can act as a safety by preventing possibilities of over-insertion during implantation.

As shown in FIG. 3C, support member 34 can include an abutment member 73 that extends from the inner surface 50 along the distal direction. It will be appreciated that the abutment member 73 can be configured to abut a force transfer member 424 (see FIG. 6D) of the spacer 30 that receives forces from the frame 26, and transfers the received forces to the cortical spacer body 41, as will be described in more detail below. In certain embodiments, the abutment member 73 can further be sized to be inserted into a force transfer channel 418 (see FIG. 6B) in the cancellous spacer body 412 so as to abut the force transfer member 424. The abutment member 73 is illustrated as a spike though it should be appreciated, that the abutment member 73 can have other shapes as desired. For instance, the abutment member 73 can have a pointed or a rounded abutment surface that abuts the force transfer member 424 as desired.

As shown in FIGS. 2A, and 3A-3E, the first arm 38 and the second arm 42 each extend from the support member 34 and define a first distal terminal end 83 and a second distal terminal end 84, respectively. The first and second arms 38 and 42 each define gripping portions and support portions. The gripping portions are configured to retain the spacer 30 while the support portions are configured to support the vertebral bodies 10 a and 10 b relative to each other. The gripping portions and the support portions can be a single structure or the support portions can be separate structures that extend from the gripping portions. The arms 38 and 42 can be radiolucent so as to increase fluoroscopy visibility. The first arm 38 includes a first inner spacer contacting surface 88 and the second arm 42 includes a second inner spacer contacting surface 92 that is spaced from the first inner spacer contacting surface 88 along a first direction, such as the lateral direction A. The inner surface of the support member 34, the first inner spacer contacting surface 88, and the second inner spacer contacting surface 92 together define a void 94 that is configured to receive and grip the spacer 30. The terminal ends 83 and 84 are spaced apart from the support member along a second direction, such as the longitudinal direction L that is substantially perpendicular to the first direction so as to define first and second lengths L₁ and L₂, respectively of the first and second arms 38 and 42. The first and second arms 38 and 42 are sized such that the first and second lengths L₁ and L₂ are each greater than a length L₃ defined between an anterior end E of the inferior vertebral body 10 b and the centroid M of the surface 14 b of the inferior vertebral body 10 b, as shown in FIG. 1C. It should be appreciated, that the first and second arms 38 and 42 can also be sized such that the first and second lengths L₁ and L₂ are greater than a length defined between an anterior end of the superior vertebral body 10 a and a centroid of the surface 14 a of the superior vertebral body 10 a. The first and second lengths L₁ and L₂ may be between about 3.5 mm and about 12 mm, between about 6.0 mm and about 10 mm, and preferably about 9.5 mm. In some embodiments, the support member 34, the first arm 38, and the second arm 42 extend around at least 51% of the spacer 30, and preferably around at least 80% of the spacer 30.

The flexible arms 38 and 42 can have a transverse height and a lateral width that at least partially define a cross-sectional area of the arms 38 and 42. The arms 38 and 42 can have a cross-sectional area that may vary so long as the arms 38 and 42 are capable of elastically deforming or flexing to thereby allow the frame 26 to receive the spacer and subsequently apply a retention force to the spacer 30 after the frame 26 has received the spacer 30. In that regard, the arms 38 and 42 are configured to elastically flex laterally outwardly away from each other, or otherwise elastically deform from a first position to a second flexed position to allow the frame 26 to receive the spacer 30. It should be appreciated that the first position can be a relaxed position of the arms 38 and 42 or a flexed position of the arms 38 and 42 that is outwardly flexed with respect to a relaxed position. At least respective portions of the arms 38 and 42, such as contact locations 320 and 324 (see FIG. 6E), are further spaced from each other in the second position than when in the first position. Once the spacer 30 is disposed between the arms 38 and 42, the arms 38 and 42 may flex inwardly toward each other to a third or engaged position whereby the arms 38 and 42 engage the spacer 30 so as to secure the frame 26 to the spacer 30 as shown in FIG. 2. It should be appreciated that the third position can be outwardly flexed with respect to the first position, and can be substantially equal to the first position. Thus, the respective portions of the arms 38 and 42 can be further spaced from each other when in the third position with respect to the first position, or the respective portions of the arms 38 and 42 can be spaced from each other when in the third position a distance substantially equal to the distance that the respective portions of the arms 38 and 42 are spaced when in the first position. Thus, it can be said that when the arms 38 and 42 are in the third position, at least respective portions of the arms 38 and 42 are spaced apart a distance equal to or greater than (or no less than) the distance that the arms 38 and 42 are spaced when in the first position. It will be further appreciated from the description below in accordance with certain embodiments (see, for instance FIG. 14C) that at least respective portions of the arms 38 and 42 can be spaced apart a distance when in the engaged position that is less than the distance that the respective portions of the arms 38 and 42 are spaced apart when in the first position.

As shown in FIG. 3C, the first and second arms 38 and 42 extend from the support member 34 such that the first and second arms 38 and 42 are angled toward each other so as to push the spacer 30 toward the other of the first and second arms 38 and 42 and toward the support member 34. For example, the inner surface of the support member 34 and the first inner spacer contacting surface 88 form an angle Ø₁ that is less than 90 degrees, and the inner surface 50 of the support member 34 and the second inner spacer contacting surface 92 form an angle Ø₂ that is less than 90 degrees. In the illustrated embodiment, Ø₁ and Ø₂ are each about 88 degrees, though it should be appreciated that Ø₁ and Ø₂ may be any angle as desired, and may be different angles with respect to each other.

As shown in FIGS. 3C and 3D, each arm 38 and 42 includes a substantially straight portion 100 that extends from the support member 34, and a distal bent or angled portion 104 that extends from a distal end of the straight portion 100 toward the other of the bent portions 104 such that the bent portions 104 are configured to contact a distal surface of the spacer 30. As shown, the bent portions 104 at least partially wrap around the spacer 30 to thereby prevent the spacer 30 from separating from the frame 26 after the spacer 30 has been retained by the frame 26. As shown in FIG. 3A, each arm 38 and 42 can include at least one retention member 116, such as a plurality of retention members 116 that extend out from the first and second inner spacer contacting surfaces 88 and 92. The retention members 116 can be arranged in a respective first column supported by the first arm 38, and a second column supported by the second arm 42. In the illustrated embodiment, the retention members 116 define teeth that extend out of the bent portions 104 so as to form a column of teeth on each bent portion 104. The retention members 116 are configured to engage the spacer 30 when the frame 22 is retaining the spacer 30 to thereby ensure that the spacer 30 remains retained by the frame 22. It should be appreciated, however, that the retention member 116 can have any configuration as desired, so long as the retention member 116 is capable of engaging the spacer 30. For example, the retention members 116 can be configured as spikes that extend from the inner surfaces 88 and 92 at an angle, elongate blades, punches that can be punched into the spacer 30 by an individual after the spacer 30 is disposed in the frame 26, or any suitable roughened surface, grit-blasted surface, or knurled surface that is configured to engage the spacer 30 and thereby retain the spacer 30.

Referring to FIG. 6A, the spacer 30 defines a proximal end surface 30 a and a distal end surface 30 b that is spaced from the proximal end surface 30 a in the distal direction along the longitudinal direction L. The spacer 30 further defines a pair of opposed side surfaces 30 c spaced from each other along the lateral direction A. The spacer 30 further defines a top surface 30 d and a bottom surface 30 e spaced from the top surface 30 d in the transverse direction T. The spacer 30 can define a plurality of grooves 415 that can extend into the side surfaces 30 c at the cortical spacer body 410, and the distal end surface 30 b. The grooves can extend at least into the spacer 30 along the transverse direction T, and can extend through the spacer 30 along the transverse direction T. The retention members 116 supported by the first arm 38 are configured to be inserted into the grooves 415 at a first one of the side surfaces 30 c. The retention members 116 supported by the second arm 42 are configured to be inserted into the grooves 415 at the second one of the side surfaces 30 c.

Referring now to FIGS. 3C-3D and 2C, the retention members 116 can define a proximal surface 116 a and a distal surface 116 b that each extend from the respective inner surfaces 88 and 92 of the corresponding first and second arms 38 and 42. The proximal surface and distal surfaces 116 a and 116 b can converge toward each other and can adjoin each other at a tip 116 c. The proximal surface can define a concavity as illustrated in FIG. 2C. The distal surface 116 b be substantially linear. For instance, the distal surface 116 b can be oriented along the lateral direction A. The tip 116 c can be offset in the distal direction with respect to a location of the inner surface from which the proximal surface 116 a extends. As illustrated in FIG. 2D, the proximal surface 116 a can be substantially linear. For instance, the proximal surface 116 a can be angled with respect to the lateral direction A. In one example, the proximal surface 116 a can be oriented so as to extend in both the distal direction and the lateral direction A as it extends from the respective inner surface toward the tip 116 c. The distal surface 116 b can be convex as it extends from the respective inner surface toward the tip 116 c. Referring to FIG. 2E, the proximal surface 116 a be substantially linear. For instance, the proximal surface 116 a can be oriented along the lateral direction A. The distal surface 116 b can be convex as it extends from the respective inner surface toward the tip 116 c. As illustrated in FIG. 2F, the proximal surface 116 a can be concave as it extends out from the respective inner surface toward the tip 116 c. The distal surface 116 b can be convex as it extends out from the respective inner surface toward the tip 116 c. The tip 116 c can be offset in the proximal direction with respect to a location of the inner surface from which the proximal surface 116 a extends. Each of the retention members 116 can overlap the spacer within the groove 415 by any distance as desired. For instance, each of the retention members 116 can overlap the spacer within the groove 415 by a distance between and including approximately 0.5 mm and approximately 4.0 mm. As a function of the length of the spacer 30 along the longitudinal direction L, the overlap can be within the range of 25% and 100% of the length of the spacer 30 in the longitudinal direction L. For instance, the overlap can be within the range of 40% and 80% of the length of the spacer 30 in the longitudinal direction L.

As shown in FIG. 3D, the arms 38 and 42 may be configured to assist in bearing compressive loads by the vertebral bodies 10 a and 10 b to thereby mitigate subsidence and settling. As shown, each arm 38 and 42 defines a respective distal portion 110 and a respective proximal portion 114. The distal portions 110 are spaced apart from the proximal portions 114 along the longitudinal direction L such that when the frame 26 is disposed in the intervertebral space 18, the distal portions 110 are on the posterior or distal side of the centroid M of the surface 14 b of the inferior vertebral body 10 b, and the proximal portions 114 are on the anterior or proximal side of the centroid M of the surface 14 b of the inferior vertebral body 10 b. Each distal portion 110 can define a superior vertebral body contacting surface 118 and an inferior vertebral body contacting surface 122. Similarly, each proximal portion 114 can define a superior vertebral body contacting surface 126 and an inferior vertebral body contacting surface 130. Because of the length of the arms 38 and 42 and because of the transverse height of the arms 38 and 42 at their distal and proximal portions, the frame 26 can bear compressive loads from the vertebral bodies if the spacer 30 were to compress.

As shown in FIG. 3D, the arms 38 and 42 may be configured to conform to the lordotic curve of the spine and in particular of the intervertebral space 18 in which the frame 26 is to be disposed. For example, a line drawn between the superior vertebral body contacting surfaces 118 and 126 of the first arm 38 forms an angle that is between about 0 degrees and about −5 degrees with respect to the insertion direction I, and a line drawn between the inferior vertebral body contacting surfaces 122 and 130 of the first arm forms a line that is between about 0 degrees and about 5 degrees with respect to the insertion direction I. Similarly, a line drawn between the superior vertebral body contacting surfaces 118 and 126 of the second arm 42 forms an angle that is between about 0 degrees and about −5 degrees with respect to the insertion direction, and a line drawn between the inferior vertebral body contacting surfaces 122 and 130 of the second arm 42 forms an angle that is between about 0 degrees and about 5 degrees with respect to the insertion direction I. It should be appreciated, however, that the lines drawn between the superior vertebral body contacting surfaces 118 and 126, and between the inferior vertebral body contacting surfaces 122 and 130 can be any angle as desired. For example, the lines may be parallel to each other. Therefore, it can be said that a first plane is defined by the superior vertebral body contacting surfaces, and a second plane is defined by the inferior vertebral body contacting surfaces. The first plane and the second plane can be parallel to each other or converge toward each other.

As shown in FIG. 3D, each arm 38 and 42 can further include a superior cut-out 140 and an inferior cut-out 144 to thereby provide visual access to the superior vertebral body 10 a and to the inferior vertebral body 10 b respectively when the frame 26 is disposed in the intervertebral space 18. The cut-outs 140 and 144 are each disposed between the proximal portions 114 and distal portions 110 of the first and second arms 38 and 42. As shown, the superior cut-outs 140 extend laterally through an upper portion of the arms 38 and 42 so as to define upper curved recesses 148 in the straight portions 100 of the arms 38 and 42. Similarly, the inferior cut-outs 144 extend laterally through a lower portion of the arms 38 and 42 so as to define lower curved recesses 152 in the arms 38 and 42. It should be appreciated that the superior and inferior cut-outs 140 and 144 can have other configurations as desired. For example, the cut-outs 140 and 144 can define rectangular channels that extend through the arms 38 and 42.

As shown in FIGS. 3D and 3E, each arm 38 and 42 can further include a window 156 that extends laterally through the straight portions 100 of the arms 38 and 42 between the superior and inferior cut-outs 140 and 144. The windows 156 are configured to provide visual access to the spacer 30 through the first and second arms 38 and 42 when the frame 26 is retaining the spacer 30. As shown, the windows 156 are oval shaped and elongate along the longitudinal direction L. It should be appreciated, however, that the windows 156 can have any shape as desired. For example, the windows 156 can also be rectangular shaped.

As shown in FIGS. 3A, 3D, and 3E, each arm 38 and 42 can include an engagement member 170 that is configured to receive a first and a second external expansion force, respectively, from an expansion instrument prior to insertion of the spacer 30 into the void 94 such that at least one of the first and second arms 38 and 42 elastically expands or elastically flexes with respect to the other of the first and second arms 38 and 42 in response to the expansion forces. As shown in FIG. 3A, the engagement members 170 each define a dove-tailed slot 174 that defines an opening 178 at its distal end such that the expansion instrument can engage the dove-tailed slot 174 in a direction that is opposite to the insertion direction I of the frame 26, thereby securing the expansion instrument to the dove-tailed slot 174. As shown in FIG. 3D, the dove-tailed slots 174 are wider at the openings 178 and taper as they extend proximally. The wider openings 178 provide a guide for the expansion instrument to engage the engagement members 170. As shown in FIG. 3A, the dove-tailed slots 174 each include a pair of opposed recesses 182 that define angled engagement surfaces 186. It should be appreciated, however, that the engagement members 170 can have any configuration as desired so long as they can receive respective expansion forces.

Referring now to FIG. 3F, and as descried above, the support member 34 can include at least one tab 64, for instance a plurality of tabs 64, that extend from the body 46. In one example, the tabs 64 can include at least a first tab 64 a and a second tab 64 b that each extends from the body 35 in the upward or superior direction. Thus, the first and second tabs 64 a and 64 b can be referred to as a first pair of tabs. The first tab 64 a and the second tab 64 b can be spaced from each other along the lateral direction A, such that the support member 34 defines a first gap 65 a between the first and second tabs 64 a and 64 b along the lateral direction. The first gap 65 a can be sized or otherwise configured to receive a portion of the first vertebral body when the first and second arms 38 and 42 are inserted into the intervertebral space. In particular, the first tab is spaced from second tab 64 b by a first distance G1 along the lateral direction A. The first distance G1 can be any distance so long as a portion of the first vertebral body can extend into the gap 65 a.

With continued reference to FIG. 3F, the tabs 64 can include at least a third tab 64 c and a fourth tab 64 d that each extends from the body 35 in the downward or inferior direction. Thus, the third and fourth tabs 64 c and 64 d can be referred to as a second pair of tabs. The third tab 64 c and the fourth tab 64 d can be spaced from each other along the lateral direction A, such that the support member 34 defines a second gap 65 b between the third and fourth tabs 64 c and 64 d along the lateral direction. The second gap 65 b can be sized or otherwise configured to receive a portion of the second vertebral body when the first and second arms 38 and 42 are inserted into the intervertebral space. In particular, the third tab 64 c is spaced from fourth tab 64 d by a second distance G2 along the lateral direction A. As shown, the second distance G2 can be less than the first distance G1. It should be appreciated, however, that the first and second distances G1 and G2 can substantially the same or the second distance G2 can be greater than the first distance G1, as desired. The first and second tabs 64 a and 64 b can be equidistant from a centerline of the frame 26, and the third and fourth tabs 64 c and 64 d can be equidistant from the centerline of the frame 26. The centerline of the frame can extend in the transverse direction T and bifurcate the frame 26 in the lateral direction A. It should be appreciated, however, that the tabs 64 can be alternatively positioned as desired. Each of the third and fourth tabs 64 c and 64 d can be spaced from the centerline a distance that is less than the distance that each of the first and second tabs 64 a and 64 b is spaced from the centerline.

Each of the tabs 64 a-64 d defines a front surface and an opposed bone contacting surface. The front surfaces of each tab 64 a-64 d can be flush with or otherwise coincident with the outer surface 54 as illustrated. It should be appreciated, however, that the front surfaces can be offset with respect to the outer surface 54 as desired. The bone contacting surfaces of the first and second tabs 64 a and 64 b are configured to abut the first vertebral body and the bone contacting surfaces of the third and fourth tabs 64 c and 64 d are configured to abut the second vertebral body when the first and second arms 38 and 42 are inserted into the intervertebral space. When the frame 26 is implanted into the intervertebral space, anterior surfaces of the first and second vertebral bodies can extend into the first and second gaps 65 a and 65 b. Further, the first and second vertebral bodies can be flush with or extend beyond the front faces of the tabs 64 a-64 d. Accordingly, it can be said that the frame 26 provides a zero profile at a centerline of the vertebral bodies when the arms 38 and 42 are inserted into the intervertebral space. The frame 26, and alternative embodiments thereof, are described in U.S. patent application Ser. No. 13/767,097 filed Feb. 14, 2013, the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein.

As shown in FIGS. 5A-5E, the spacer 30 can be coupled to the frame 26 using an actuation instrument 210 that is configured as an expansion instrument. The instrument 210, the frame 26, and in some cases the spacer 30 can together define an intervertebral implant system 214. The expansion instrument 210 includes a grip 212 and a handle 213. The grip 212 is configured as an expansion grip and is configured to apply the first and second expansion forces to the engagement members 170 of the first and second arms 38 and 42. The first and second expansion forces will elastically expand the first and second arms 38 and 42 of the frame 26 to thereby allow the spacer 30 to be received by the void 94 of the frame 26.

As shown, the instrument 210 includes a first arm 220 that is configured to releasably couple to the first arm 38 of the frame 26, and a second arm 224 that is rotatably coupled to the first arm 220 at a first pivot 228 and is configured to releasably couple to the second arm 42 of the frame 26. The first and second arms 220 and 224 are configured as expansions arms. The first and second expansion arms 220 and 224 are pivotally coupled to each other at the first pivot 228 such that rotation of the first and second expansion arms 220 and 224 about the first pivot 228 causes the first and second arms 38 and 42 of the frame 26 to elastically flex away from each other when the instrument 210 is coupled to the frame 26. Therefore, the instrument 210 is configured to have a first position or configuration whereby the instrument 210 can be coupled to the frame 26, and a second position or configuration whereby the instrument 210 is applying expansion forces to the arms 38 and 42 of the frame 26 so that the frame can receive the spacer 30.

As shown in FIGS. 5B and 5C, each expansion arm 220 and 224 includes a handle portion 232 that extends proximally from the first pivot 228 and a gripping portion 236 that extends distally from the first pivot 228. The handle portions 232 define the handle 213, and the gripping portions 236 define the grip 212. The handle portions 232 are configured to be gripped by an individual such that the handle portions 232 can be squeezed or otherwise moved toward each other. The expansion instrument 210 can further include a handle locking mechanism 240 that is configured to lock the handle portions 232 relative to each other after the handle portions 232 have been moved toward each other. In the illustrated embodiment, the locking mechanism 240 includes a threaded shaft 244 and a nut 248. As at least one of the handle portions 232 is moved along the shaft 244, the nut 248 can be threaded along the shaft 244 to thereby lock the handle portions 232 relative to each other. It should be appreciated, however, that the locking mechanism 240 can include other configurations, as desired. For example, the locking mechanism 240 can have a ratchet configuration.

As shown in FIGS. 5C and 5D, the gripping portions 236 are configured to expand the frame arms as the handle portions 232 are moved toward each other. Each gripping portion 236 includes an extension member 250 that extends distally from the first pivot 228, and a gripping member 254 that is pivotally coupled to a distal end of the extension member 250 at a second pivot 258. Each gripping member 254 includes an engagement member 262 that is configured to engage respective engagement members 170 of the first and second arms 38 and 42 of the frame 26. As shown in FIG. 5D, the engagement members 262 are dove-tailed members 266 that are opposed to each other and are configured to mate with the dove-tailed slots of the first and second arms 38 and 42 to thereby couple the expansion instrument 210 to the frame 26. As shown, each dove-tailed member 266 includes a pair of transversely opposed protrusions 280 that each defines an angled engagement surface 284 that is configured to abut or otherwise contact a respective angled engagement surface 186 of the slots 174 when the engagement members 262 are mated with the engagement members 170. It should be appreciated that the engagement members 262 can have other configurations as desired. For example, the engagement members 262 and the engagement members 170 can be reversed.

As shown in FIG. 5D, a proximal end of each engagement member 262 defines a tapered lead-in portion 270 that allows the engagement members 262 to easily be guided into the openings 178 of the engagement members 170. Therefore, the expansion instrument 210 can easily be coupled to the frame 26 along a direction that is opposite the insertion direction I. That is, if the frame 26 is stationary, the expansion instrument 210 can be coupled to the frame 26 by translating the instrument 210 along a direction that is opposite the insertion direction I.

As shown in FIG. 5C, each gripping member 254 includes a pair of stops 300 that extend proximally toward the extension member 250 and are spaced apart from the extension member 250. As the gripping member 254 rotates about the second pivot 258 the stops 300 will limit the rotation by contacting the extension member 250. Therefore, the angular range in which the gripping members 254 can rotate about the second pivots 258 will depend on the distance in which the stops 300 are spaced apart from the extension members 250.

As shown in FIG. 5C, each gripping portion 236 further includes a biasing member 304 that is configured to bias the gripping members 254 toward each other. In the illustrated embodiment, the biasing members 304 are leaf springs 308 that are coupled to the extension members 250 and urge against an outer surface of the gripping members 304. By biasing the gripping members 254 toward each other, the expansion instrument 210 can more easily and more predictably be coupled to the frame 26. It should be appreciated, however, that the biasing members 304 can have other configurations as desired. For example, the biasing members can be elastically flexible wires and can be disposed within the gripping members 254 as desired.

In operation and in reference to FIG. 5E, the expansion instrument 210 is coupled to the frame 26 by placing the engagement members 262 of the instrument 210 distal to the engagement members 170 of the frame 26. By translating or otherwise moving the frame 26 or the instrument 210 toward the other, the engagement members 262 will engage the engagement members 170 to thereby couple the frame 26 to the instrument 210 such that the second pivots 258 of the instrument 210 abut an outer surface of the flexible arms 38 and 42 proximate to the support member 34. By squeezing the handle portions 232 toward each other, the extension member 250 of the first expansion arm 220 will rotate counterclockwise about the first pivot 228 and the gripping member 254 of the first expansion arm 220 will rotate clockwise about the second pivot 258. Conversely, the extension member 250 of the second expansion arm 224 will rotate clockwise about the first pivot 228 and the gripping member 254 of the second expansion arm 224 will rotate counterclockwise about the second pivot 258.

This rotation will cause at least one of the first and second arms 38 and 42 to elastically flex away from the other. For example, the first and second inner spacer contacting surfaces 88 and 92 of the first and second arms 38 and 42 can define respective first and second respective contact locations 320 and 324, and at least one of the first and second arms 38 and 42 is flexible so as to be movable between a first position, whereby the frame 26 defines a first distance d₁ that extends along the lateral direction A between the first and second contact locations 320 and 324, and a second position, whereby the frame 26 defines a second distance d₂ that extends along the lateral direction A between the first and second contact locations 320 and 324. It should be appreciated that the first and second contact locations 320 and 324 can be located anywhere along the arms 320 and 324 so long as they remain the same when the first and second distances are measured.

As shown in FIG. 5E, the second distance d₂ is greater than the first distance d₁ such that when in the second position, the void 94 defines a cross-sectional dimension that is greater than that of the spacer 30 such that the void 94 is sized to receive the spacer 30. While the arms 38 and 42 are elastically flexed, at least one of the arms 38 and 42 is biased toward the first position. Therefore, when the handle portions 232 of the instrument 210 are released, the arms 38 and 42 will flex back to a third position, and when in the third position, the frame 26 defines a third distance d₃ that extends along the lateral direction A between the first and second contact locations 320 and 324 and is less than the second distance d₂ (See FIG. 2B). When in the third position at least one of the first and second inner contacting surfaces 88 and 92 of the arms 38 and 42 will apply a retention force against the spacer 30 along a direction toward the other of the first and second inner spacer contacting surfaces 88 and 92.

Referring now to FIGS. 5F-5J, the spacer 30 can be coupled to the frame 26 using an actuation instrument 510 that is configured as an expansion instrument in accordance with an alternative embodiment. Thus, the instrument 510, the frame 26, and in some cases the spacer 30 can together define an intervertebral implant system 514. The expansion instrument 510 includes first and second members 510 a and 510 b that are configured to engage each other so as to define a grip 512 and a handle 523. The grip 512 is configured as an expansion grip and is configured to apply the first and second expansion forces to the engagement members 170 of the first and second arms 38 and 42. The first and second expansion forces will elastically expand the first and second arms 38 and 42 of the frame 26 to thereby allow the spacer 30 to be received by the void 94 of the frame 26.

As shown, the first member 510 a includes a first arm 520 that is configured to releasably couple to the first arm 38 of the frame 26. The second member 510 b includes a second arm 524 that is configured to releasably couple to the second arm 42 of the frame 26. The first and second arms 520 and 524 are configured as expansions arms. The first and second expansion arms 520 and 524 are pivotally coupled to each other such that rotation of the first and second expansion arms 520 and 524 with respect to each other about respective pivot locations causes the first and second arms 38 and 42 of the frame 26 to elastically flex away from each other when the instrument 510 is coupled to the frame 26. Therefore, the instrument 510 is configured to have a first position or configuration whereby the instrument 510 can be coupled to the frame 26, and a second position or configuration whereby the instrument 510 is applying expansion forces to the arms 38 and 42 of the frame 26 so that the frame can receive the spacer 30.

The first member 510 a defines a first base 511 a, such that the first arm 520 generally extends from the first base 511 a in a distal direction. The first arm 520 can be monolithic with the first base 511 a. For instance, the first base 511 a and the first arm 520 can be made from the same material. The material can be metal. Alternatively, the material can be plastic. Alternatively, the first arm 520 can be attached to the first base 511 a in any manner desired. In this regard, the first base 511 a and the first arm 520 can be made from different materials. For example, the first base 511 a can be plastic, and the first arm 520 can be a metal. Alternatively, the first base 511 a can a metal, and the first arm 520 can be a plastic. The first member 510 a can define a first gap 513 a that extends into the first base so as to define corresponding first and second portions 515 a and 517 a that are separated from each other by the first gap 513 a. The first member portion 515 a can be an upper portion, and the second portion 517 a can be a lower portion that is spaced from the upper portion 515 a in a downward direction. At least a portion of the first gap 513 a can extend into the first base 511 a but not through the first base 511 a, so as to terminate at a first stop wall 519 a.

Similarly, the second member 510 b defines a second base 511 b, such that the second arm 524 generally extends from the second base 511 b in the distal direction. The second arm 524 can be monolithic with the second base 511 b. For instance, the second base 511 b and the second arm 524 can be made from the same material. The material can be metal. Alternatively, the material can be plastic. Alternatively, the second arm 524 can be attached to the second base 511 b in any manner desired. In this regard, the second base 511 b and the second arm 524 can be made from different materials. For example, the second base 511 b can be plastic, and the second arm 524 can be a metal. Alternatively, the second base 511 b can a metal, and the second arm 524 can be a plastic. The second member 510 b can define a second gap 513 b that extends into the second base so as to define corresponding first and second portions 515 b and 517 b that are separated from each other by the second gap 513 b. The first member portion 515 b can be an upper portion, and the second portion 517 b can be a lower portion that is spaced from the upper portion 515 b in the downward direction. At least a portion of the second gap 513 b can extend into the second base 511 b but not through the second base 511 b, so as to terminate at a second stop wall 519 b.

The first gap 513 a can be sized to receive the first portion 515 b of the second member 510 b. Alternatively or additionally, the first gap 513 can be sized to receive the second portion 517 b of the second member 510 b. Similarly, the second gap 513 b can be sized to simultaneously receive the first portion 515 a of the first member 510 a. Alternatively or additionally, the second gap 513 b can be sized to simultaneously receive the second portion 517 a of the first member 510 a. In accordance with one embodiment, the first gap 513 a is sized to receive the first portion 515 b of the second member 510 b, and the second gap 513 b is sized to simultaneously receive the second portion 517 a of the first member 510 a. The first and second bases 511 a and 511 b slide relative to each other so as to cause the respective first and second arms 520 and 524 to move away from each other. Otherwise stated, the first and second bases 511 a and 511 b can pivot with respect to each other about a pivot location that translates as the first and second bases 511 a and 511 b translate with respect to each other.

The first arm 520 is configured to releasably couple to the first arm 38 of the frame 26 such that the first member 510 a abuts a first side of the frame 26 at a first abutment. The second arm 524 is configured to releasably couple to the second arm 42 of the frame 26 such that the second member 510 b abuts a second side of the frame 26 at a second abutment. The second side of the frame 26 is opposite the first side of the frame 26 with respect to the lateral direction. In accordance with one embodiment, the first arm 520 is configured to releasably couple to the first arm 38 of the frame 26 such that the first member 510 a abuts a first side of the support member 34 at the first abutment. The second arm 524 is configured to releasably couple to the second arm 42 of the frame 26 such that the second member 510 b abuts a second side of the support member 34 at the second abutment. The first and second members 510 a and 510 b of the instrument 510 can be identical to each other in one embodiment. Alternatively, the first and second abutments can be defined by proximal ends of the first and second arms 38 and 42, respectively.

The first and second members 510 a and 510 b can define first and second handle portions 523 a and 523 b, respectively, that define the handle 523 of the instrument 510. During operation, the handle portions 523 a and 523 b can be moved toward each other, thereby causing the first gap 513 a to further receive the respective portion of the second member 510 b, and the second gap 513 b to further receive the respective portion of the first member 510 a. The handle portions 523 a and 523 b can define grips that are engaged and receive a force that biases each of the handle portions 523 a and 523 b toward the other of the handle portions 523 a and 523 b. As the first and second members 510 a and 510 b are moved toward each other, the first member 510 a pivots about the first abutment, and the second member 510 b pivots about the second abutment, thereby causing the first and second arms 520 and 524 to move away from each other. When the first and second arms 520 and 524 are coupled to the first and second arms 38 and 42, respectively, of the frame 26, movement of the first and second arms 520 a and 524 away from each other causes the first and second arms 38 and 42 to move from the first position to the second position described above.

The instrument 510 can include a force limiter that limits the amount of force applied to the first and second arms 38 and 42 of the frame 26 that expands the first and second arms 38 and 42 from the first position to the second position. In particular, the portion of the second member 510 b that is received in the first gap 513 a is configured to abut the first stop wall 519 a, thereby preventing additional movement of the handle portions 523 a and 523 b toward each other. Alternatively or additionally, the portion of the first member 510 a that is received in the second gap 513 b is configured to abut the second stop wall 519 b, thereby preventing additional movement of the handle portions 523 a and 523 b toward each other. Thus, during operation, the handle portions 523 a and 523 b can be moved toward each other until one or both of the first and second members 510 a and 510 b abuts the second and first stop walls 519 b and 519 a, respectively.

As described above, the first and second arms 520 and 524 of the instrument 510 is configured to releasably couple to the first and second arms 38 and 42, respectively, of the frame 26 such that movement of the first and second arms 520 and 524 away from each other applies a first to the first and second arms 38 and 42 that causes the first and second arms 38 and 42 to move from the first position to the second position. In particular, the instrument 510 defines a grip 512 that is configured to releasably couple to the engagement members 170 of the first and second arms 38 and 42, respectively, of the frame 26. The grip 512 can include gripping portions supported by the first and second arms 520 and 524, respectively, that are configured to releasably couple to the engagement members 170 of the first and second arms 38 and 42, respectively, of the frame 26. The gripping portions 536 are configured to expand the frame arms 38 and 42 as the handle portions 523 a and 523 b are moved toward each other.

Each gripping portion 536, and thus each of the first and second arms 520 and 524, can include an engagement member 562 that is configured to engage the respective engagement members 170 of the first and second arms 38 and 42 of the frame 26, thereby attaching the arms 520 and 524 to the first and second arms 38 and 42, respectively. The engagement members 562 can be dove-tailed members 566 that are opposed to each other and are configured to mate with the dove-tailed slots of the first and second arms 38 and 42 to thereby releasably couple the expansion instrument 510 to the frame 26. As shown, each of the dove-tailed members 566 includes a protrusion 580 such that the protrusions 580 are opposite each other. Each of the protrusions 580 defines an angled engagement surface 584 that is configured to abut or otherwise contact a respective angled engagement surface 186 of the slots 174 when the engagement members 562 are mated with the engagement members 170. It should be appreciated that the engagement members 562 can have other configurations as desired. For example, the geometry of the engagement members 562 and the engagement members 170 can be reversed. A proximal end of each engagement member 562 can define a tapered lead-in portion 570 that allows the engagement members 562 to easily be guided into the openings 178 of the engagement members 170. Therefore, the expansion instrument 510 can be inserted into the openings 178 in a first direction so as to releasably couple the instrument 510 to the frame 26. Similarly, the expansion instrument 510 can be removed from the openings 178 in a second direction opposite the first direction so as to decouple the instrument 510 from the frame 26. It should be appreciated that the expansion instrument 510 can be assembled with the frame 26, and that the frame 26 can retain the spacer 30 or not retain the spacer 30 when the expansion instrument is assembled with the frame 26.

Referring to FIGS. 6A-6D, and the spacer 30 defines a proximal end surface 30 a and a distal end surface 30 b that is spaced from the proximal end surface 30 a along the longitudinal direction L. For instance, the distal end surface 30 b is spaced from the proximal end surface 30 a in the distal direction. Thus, the distal end surface 30 b can be spaced from the proximal end 30 a in the insertion direction of the spacer 30 into the intervertebral space. Accordingly, the distal end surface 30 b can be spaced from the proximal end 30 a in the insertion direction of the intervertebral implant 22 into the intervertebral space. It should be appreciated that, when the implant 22, and thus the spacer 30, is implanted in the intervertebral space, the distal end surface 30 b is spaced posteriorly from the proximal end surface 30 a.

The spacer 30 further defines a pair of opposed side surfaces 30 c spaced from each other along the lateral direction A. Each of the side surfaces 30 c further extends from the proximal end surface 30 a to the distal end surface 30 b. When the frame 26 is attached to the spacer 30 (see FIGS. 2A-B and 11B-C), the support member 34 can extend along the proximal end surface 30 a, and the arms 38 and 42 can extend along at least a portion up to an entirety of the length along the longitudinal direction L of respective different ones of the sides 30 c. It should be appreciated that the surfaces 30 a-30 e can be sized and shaped as desired. For instance at least one or more up to all of the surfaces 30 a-30 e can be planar, curved, bent, or otherwise non-planar as desired.

The spacer 30 further defines a top surface 30 d and a bottom surface 30 e spaced from the top surface 30 d along the transverse direction T. For instance, the top surface 30 d is spaced upward with respect to the bottom surface 30 e. Thus, the top surface 30 d is configured to face the superior vertebral surface 14 a of the superior vertebral body 10 a, and contact the superior vertebral surface 14 a of the superior vertebral body 10 a. The bottom surface 30 e is configured to face the inferior vertebral surface 14 b of the inferior vertebral body 10 b, and contact the inferior vertebral surface 14 b of the inferior vertebral body 10 b. The spacer 30 can define a height from the top surface 30 c to the bottom surface 30 d in the transverse direction T. The spacer can further define a length from the proximal end surface 30 a to the distal end surface 30 b in the longitudinal direction. The distal end surface 30 b can define a first width along the lateral direction A that is less than a second width along the lateral direction A of the proximal end surface 30 a. Each of the first and second widths can extend along the lateral direction A from one of the side surfaces 30 c to the other of the side surfaces 30 c. At least one or both of the first and second widths can be greater than the height and less than the length.

As described above, the spacer 30 can be made from a bone graft material such as allograft bone, autograft bone, or xenograft bone, for example. For instance, the spacer 30 can include a cortical spacer body 410 and a cancellous spacer body 412. The cortical spacer body 410 can define at least a portion up to an entirety of the distal end surface 30 b. The cancellous spacer body 412 can define at least a portion up to an entirety of the proximal end surface 30 a. It will be appreciated that the a fixation member, such as a screw, that is inserted through the fixation element receiving aperture 58 (see FIGS. 3A-3C) toward the spacer 30 travels from the support member 34 and through the cancellous spacer body 412, and thus through the cancellous bone graft material, without passing through cortical spacer body 410, and thus without passing through any of the cortical bone graft material. Thus, a straight line passing centrally through the fixation element receiving apertures 58 is aligned with the cancellous spacer body 412 without first passing through the cortical spacer body 410. The cortical spacer body 410 can further define a first portion of one or both of the side surfaces 30 c, and the cancellous spacer body 412 can define a second portion of one or both of the side surfaces 30 c. The first portion of the side surfaces 30 c can be distal with respect to the second portion of the side surfaces 30 c. Similarly, the cortical spacer body 410 can further define a first portion of either or both of the top and bottom surfaces 30 d and 30 e. The cancellous spacer body 412 can define a second portion of either or both of the top and bottom surfaces 30 d and 30 e. The first portion of the top and bottom surfaces 30 d and 30 e can be distal with respect to the second portion of the top and bottom surfaces 30 d and 30 e.

The cortical spacer body 410 and the cancellous spacer body 412 are configured to abut each other so as to define the spacer 30. For instance, the cortical spacer body 410 can include an engagement member 414, and the cancellous spacer body 412 can include an engagement member 416 that is configured to engage with the engagement member 414 of the cortical spacer body 410 so as to join the cortical spacer body 410 to the cancellous spacer body 412. In this regard, the engagement member 414 of the cortical spacer body 410 can be referred to as a first engagement member, and the engagement member 416 of the cancellous spacer body 412 can be referred to as a second engagement member. The first engagement member 414 can be disposed distal with respect to the second engagement member 416. Further, the first and second engagement members 414 and 416 can overlap along the longitudinal direction L such that a straight line that extends in the distal direction from the proximal end surface 30 a can pass through both the first engagement member 414 and the second engagement member 416.

In accordance with one embodiment, the first engagement member 414 can define a recess 419, and the second engagement member 416 be configured as a projection 420 that is sized to be received in the recess 419. Otherwise sated, the recess 419 is sized to receive the projection 420. Thus, the recess 419 defined by the first engagement member 414 is sized to receive the second engagement member 416. The first engagement member 414 can be defined by a base 414 a and a pair of necked portions 414 b that extend out from the base 414 a in the distal direction and project inward in opposite directions toward each other along the lateral direction A. The base 414 a and the necked portions 414 b can define the recess 419. The recess 419 can extend through the cortical spacer body 410 along the transverse direction T. The second engagement member 416 can include a base 416 a and at least one wing 416 b, such as a pair of wings 416 b, that extend from the base 416 a in the proximal direction, and project out with respect to the stem 416 a in opposite directions away from each other along the lateral direction A. The wings 416 b can thus be disposed between the necked portions 414 b and the base 414 a. Similarly, the necked portions 414 b can be disposed between the wings 416 b and the base 416 a. Accordingly, the second engagement member 416 is surrounded by the first engagement member 414 along the lateral direction A and in the distal direction. Otherwise stated, the first engagement member 414 surrounds the second engagement member 416 along the lateral direction A and in the distal direction. It can thus be said that the cortical spacer body 410 can partially surround the cancellous body portion 412.

Thus, when the first and second engagement members 414 and 416 engage each other so as to join the cortical spacer body 410 to the cancellous spacer body 412, the engagement members 414 and 416 interfere with each other along both the longitudinal direction L and the lateral direction A. The interference thus prevents removal of the cortical spacer body 410 and the cancellous spacer body 412 along the longitudinal and lateral directions. Rather, in order to remove the cortical spacer body 410 and the cancellous spacer body 412 from each other, the cortical spacer body 410 and the cancellous spacer body 412 are moved with respect to each other along the transverse direction T until the engagement members 414 and 416 are removed from interference with each other.

It is recognized that the cortical spacer body 410 provides structural rigidity to the spacer 30, and the cancellous spacer body 412 promotes bony ingrowth of the first and second vertebral bodies into the cancellous spacer body 412. Accordingly, it is desirable to provide a sufficiently high surface area of cancellous spacer body 412 at the top surface 30 d and the bottom surface 30 e to promote adequate bony ingrowth while providing a sufficient volume of cortical spacer body 412 to provide adequate structural rigidity for the spacer 30. The spacer 30, constructed in accordance with various embodiments described herein in with reference to FIGS. 6A-12E, can have a surface area of cancellous bone within a first range between and including approximately 40% and approximately 85% at either or both of the top and bottom surfaces 30 d and 30 e. For instance, the first range can be between and include approximately 40% and 75%, including approximately 55% and 70%. Thus, it can be said that either or both of the top and bottom surfaces 30 d and 30 e can have a surface area, and a majority of the surface area can be defined by the cancellous spacer body 412. A minority of the surface area can be defined by the cortical spacer body 410.

As illustrated in FIG. 6A, the cortical spacer body 410 can define a surface area at each of the top and bottom surfaces 30 d and 30 e as desired, for instance between 35 mm² and 60 mm², including between 40 mm² and 50 mm², for instance approximately 46 mm². The cancellous spacer body 412 can define a surface area at each of the top and bottom surfaces 30 d and 30 e as desired, for instance between 50 mm² and 100 mm², including between 70 mm² and 90 mm², for instance approximately 816 mm². The spacer 30, constructed in accordance with various embodiments described herein in with reference to FIGS. 6A-12E, can have any height from the top surface 30 c to the bottom surface 30 d as desired. It should be appreciated that the spacers 30, and thus the intervertebral implants 22, described herein can be sized as desired to be inserted into an intervertebral spacer at any location along the spine, including the cervical region, the thoracic region, and the lumbar region.

The spacer 30 further defines a force transfer channel 418 that extends through the cancellous spacer body 412. The force transfer channel 418 can terminate at the cortical spacer body 410. Alternatively, the channel 418 can extend at least into the cortical spacer body 410. For instance, the channel 418 can terminate in the cortical spacer body 410. Alternatively, the channel 418 can extend through the cortical spacer body 410. The channel 418 can have a first opening 418 a defined by the proximal end surface 30 a. Accordingly, the channel 418 can have a first end defined by the first opening 418 a. The first opening 418 a can be an enclosed opening. That is, the first opening 418 a can be enclosed by the proximal end surface 30 a along a plane defined by the lateral direction A and the transverse direction T. The first opening 418 a can be sized to receive the abutment member 73 of the frame 26 when the frame 26 is attached to the spacer 30. Thus, the abutment member 73 can extend from the first opening 418 a into the channel 418 in the distal direction.

The channel 418 has a second end opposite the first end. The second end of the channel 418 can be terminate within the cortical spacer body 410 as illustrated in FIGS. 6D and 6K, such that the first opening 418 a is the only opening of the aperture. Alternatively, as illustrated in FIGS. 6L and 6M, the channel 418 can have a second opening 418 b defined by the distal end surface 30 b. Thus, the second end of the channel 418 can be defined by the second opening 418 b. The channel 418 can therefore extend from the proximal end surface 30 a to the distal end surface 30 b. The second opening 418 b can be an enclosed opening. That is, the second opening 418 b can be enclosed by the distal end surface 30 b along a plane defined by the lateral direction A and the transverse direction T. Alternatively, the second end of the channel 418 can terminate at the cortical spacer body 410. Thus, the second opening 418 b can be defined by the cancellous spacer body 412. In one example, an entirety of the channel 418 can be enclosed by the spacer 30. That is, the entirety of the channel 418 can be enclosed between the first end of the channel 418 and the second end of the channel 418 along a plane defined by the lateral direction A and the transverse direction T. It should be appreciated, however, that at least one up to all of the first opening 418 a, the second opening 418 b, and at least a portion up to an entirety of the channel 418 between the first and second openings 418 a and 418 b can be open, and thus not completely enclosed, along a plane defined by the lateral direction A and the transverse direction T.

In one example, the channel 418 can define a central axis of elongation 422 that is equidistant with respect to each of the side surfaces 30 c. The central axis of elongation 422 can therefore bifurcate the spacer 30 into two equal halves along the lateral direction A. Thus, the central axis of elongation can be oriented in the longitudinal direction L. It should be appreciated, however, that the central axis of elongation 422 can be oriented in any suitable alternative direction as desired. For instance, the central axis of elongation 422 can be elongate in a direction that includes a directional component in the longitudinal direction L, and one or more directional components in either or both of the lateral direction A and the transverse direction T. The channel 418 can be cylindrical or can define any suitable alternative shape as desired.

With continuing reference to FIGS. 6A-6J, the spacer 30 further includes a force transfer member 424 that is configured to be inserted into the channel 418. Thus, the channel 418 is sized and configured to receive the force transfer member 424. The force transfer member 424 can be made of any suitable biocompatible material having a hardness greater than the cancellous spacer body 412. For instance, the force transfer member 424 can be made of cortical bone, titanium, steel, PEEK, a polymer, ceramics, chronOs, CoCr (or other implantable metals), ultra high molecular weight polyethylene (UHMWPE), poly ether ether ketone (PEKK), Carbon-fiber reinforced poly ether ether ketone (PEEK), other suitable implantable polymers, or the like. The force transfer member 424 defines a first end 424 a and a second end 424 b opposite the first end 424 a. The force transfer member 424 can define a length from the first end 424 a to the second end 424 b that is less than or equal to the length of the channel 418. The length can be straight and linear from the first end 424 a to the second end 424 b. The force transfer member 424 can be cylindrical in one embodiment. For instance, the force transfer member 424 can be configured as a dowel. When the force transfer member 424 is disposed in the channel 418, the first end 424 a can be positioned adjacent the first opening 418 a. In one example, the first end 424 a can be recessed with respect to the first opening 418 a along the distal direction. In another example, the first end 424 a can be flush with the proximal end surface 30 a. Thus, the first end 424 a can define a surface geometry that matches the surface geometry of the proximal end surface 30. It should be appreciated that the spacers described herein can include as many force transfer members 424 as desired. Further, the first end 424 a of one or more of the force transfer members 424 can be recessed with respect to the first opening 418 a in the distal direction. Alternatively or additionally, the first end 424 a of one or more of the force transfer members 424 can be flush with the proximal end surface 30 a. Referring also to FIG. 3C, the abutment member 73 can contact the first end 424 a when the frame 26 is attached to the spacer 30, and the force transfer member 424 is disposed in the channel 418. For instance, the abutment member 73 can be in abutment with the first end 424 a along the longitudinal direction L.

Further, when the force transfer member 424 is disposed in the channel 418, the second end 424 b can be in contact with the cortical spacer body 410. In one example, the second end 424 b can be positioned at or adjacent the second end of the channel 418. As described above, the second end of the aperture can terminate at the cortical spacer body 410 or in the cortical spacer body 410. As a result, the second end 424 b of the force transfer member can be in contact with the cortical spacer body 410. For instance, the second end 424 b can be in abutment with the cortical spacer body 410 along the direction of elongation of the force transfer member 424, such as the longitudinal direction L. Alternatively or additionally, the second end 424 b can be embedded in the cortical spacer body 410. Thus, the second end 424 b can be press-fit in the channel 418 so as to contact the cortical spacer body 410. The second end 424 b can be disposed at the second end of the channel 418. Alternatively, the second end 424 b can be recessed with respect to the second end of the channel 418, and the distal end surface 30 b, along the proximal direction. As described above, the channel 418 can alternatively extend through the spacer body from the proximal end surface 30 a to the distal end surface 30 b so as to define first and second openings 418 a and 418 b. The second end 424 b of the force transfer member 424 can extend to the second opening 418 b, and can thus be flush with the distal end surface 30 b. Accordingly, the force transfer member 424 can be press-fit in the channel 418 at the cortical spacer body 410.

During operation, as the intervertebral implant 22 is inserted into the intervertebral space, the outer surface 54 of the body 46 of the support member 34 may be impacted by an impaction tool or the like in order to advance the implant 22 into the intervertebral space. Because the abutment member 73 is in contact with the force transfer member 424, for instance in abutment contact or in press-fit contact, or both, impaction forces is transferred from the frame 26, to the force transfer member 424, through the force transfer member 424, and to the cortical spacer body 410. Thus, though the support member 34 is positioned adjacent the cancellous spacer body 412, a substantial majority up to a substantial entirety of the impaction forces are absorbed by the cortical spacer body 412, which has a rigidity greater than that of the cancellous spacer body 412.

Thus, the intervertebral implant can be fabricated by engaging the engagement member 414 of the cortical spacer body 410 with the engagement member 416 of the cancellous spacer body 412, inserting the second end 424 b of the force transfer member 424 into the first opening 418 a of the force transfer channel 418, inserting the force transfer member 424 in the channel in the distal direction until the second end 424 b contacts the cortical spacer body 410, and attaching the frame 26 to the spacer 30 such that the support member 34 extends along the proximal end surface 30 a, the abutment member 73 abuts the first end 424 a of the force transfer member and the first and second arms 38 and 42 engage so as to attach to the respective side surfaces 30 c at the cortical spacer body 410.

It should be appreciated, as illustrated in FIGS. 6D and 6L that the top surface 30 c and the bottom surface 30 can converge toward each other along the distal direction at an angle G. The angle G can be between 2 degrees and 15 degrees, for instance between 5 degrees and 10 degrees, for instance approximately 7 degrees. Thus, the top and bottom surfaces 30 d and 30 e can be geometrically configured to restore lordotic curvature to the vertebral bodies. Alternatively, as illustrated in FIGS. 6K and 6M, the top and bottom surfaces 30 d and 30 e can be parallel to each other along the longitudinal direction L.

Referring now to FIG. 6A and FIGS. 7A-7E, either or both of the top and bottom surfaces 30 d and 30 e can be smooth or can include any surface geometry as desired. The surface geometry can increase the surface area of the respective top and bottom surfaces 30 d and 30 e, thereby promoting bony ingrowth of the vertebral bodies into the top and bottom surfaces 30 d and 30 e. Further, the surface geometry can increase frictional forces between the top and bottom surfaces 10 d and 10 e and the respective superior and inferior surfaces 14 a and 14 b, thereby promoting stabilization of the spacer 30 within the intervertebral space. For instance, as illustrated in FIGS. 6A and 6D, the surface geometry can define elongate ridges 426. Each of the ridges 426 can extend out from a respective base 426 a to a respective peak 426 b. The ridges can be tapered from the base 426 a to the peak 426 b. For instance the peak 426 b can be a pointed peak or a rounded peak. The ridges 426 can be oriented parallel to each other, or angularly offset with respect to each other as desired. For instance, the ridges 426 can be elongate along the lateral direction A, or any suitable alternative direction as desired. For instance, the ridges 426 can be elongate along the longitudinal direction L. Alternatively, the ridges 426 can be elongate along a direction angularly offset with respect to each of the lateral direction A and the longitudinal direction L. The ridges 426 can extend between the side surfaces 30 c. For instance, the ridges 426 can extend from one of the side surfaces 30 c to the other of the side surfaces 30 c. The ridges 426 can further be oriented straight along the direction of elongation or curved or bent as desired. The ridges 426 can be spaced from each other uniformly or variably along a direction perpendicular to the direction of elongation of the ridges 426. Thus, the ridges 426 can be spaced from each other along the longitudinal direction L. The direction of elongation can be determined by the orientation of the ridges when the ridges 426 are oriented straight. Alternatively, the direction of elongation can be determined by a straight line that extends from one of the terminal ends of the ridges to the respective opposite terminal end of the ridges, for instance, when the ridges 426 are curved.

As illustrated in FIG. 6A, the ridges 426 can be disposed along an entirety of either or both of the top and bottom surfaces 30 d and 30 e along a direction perpendicular to the direction of elongation. For instance, the ridges 426 can be arranged from the proximal end surface 30 a to distal end surface 30 b. Alternatively, as illustrated in FIG. 7A, the ridges 426 can be disposed along a portion of either or both of the top and bottom surfaces 30 d and 30 e. For instance, the ridges 426 can be arranged along either or both of the top and bottom surfaces 30 d and 30 e of the spacer 30 at the cancellous spacer body 412, and not at the cortical body portion 410. In one example, the ridges 426 can be arranged along a portion of the cancellous spacer body 412, for instance, at a portion of the cancellous spacer body that does not include the engagement member 416. Alternatively, the ridges 426 can be arranged along an entirety of the cancellous spacer body 412. Alternatively or additionally, the ridges 426 can be arranged along a portion of the cortical spacer body 410.

Referring now to FIGS. 7B-7F. the surface geometry can alternatively or additionally include spikes 428. For instance, each of the spikes 428 can define a base 428 a and extend out from the base 428 a along the transverse direction T to a peak 428 b. Thus, the spikes 428 at the top surface 30 d can extend from the base 428 a to the peak 428 a in the upward direction, that is, away from the bottom surface 30 e. Similarly, spikes 428 at the bottom surface 30 e can extend from the base 428 a to the peak 428 a in the downward direction, that is, away from the top surface 30 d. The spikes 428 can be tapered from the base 428 a to the peak 428 b. For instance the peak 428 b can be a pointed peak or a rounded peak. The spikes 428 can be equidistantly spaced from each other along either or both of the lateral direction A and the longitudinal direction L. Alternatively or additionally, the spikes 428 can be spaced from each other variably along either or both of the both of the lateral direction A and the longitudinal direction L.

The spikes 428 can be arranged between the side surfaces 30 c, and further between the proximal end surface 30 a and the distal end surface 30 b. For instance, as illustrated in FIG. 7B, the spikes 428 can be arranged from one of the side surfaces 30 c to the other of the side surfaces 30 c. Further, the spikes 428 can be arranged from the proximal end surface 30 a to the distal end surface 30 b. Thus, the spikes 428 can be defined by both of the cortical spacer body 410 and the cancellous spacer body 412. Alternatively, the spikes 428 can be defined by one of the cortical spacer body 410 and the cancellous spacer body 412. For example, as illustrated in FIG. 7C, the spikes 428 can be disposed along a portion of either or both of the top and bottom surfaces 30 c and 30 d. For instance, the spikes 428 can be arranged along either or both of the top and bottom surfaces 30 d and 30 e of the spacer 30 at the cancellous spacer body 412, and not at the cortical body portion 410. In one example, the spikes 428 can be arranged along a portion of the cancellous spacer body 412, for instance, at a portion of the cancellous spacer body that does not include the engagement member 416. Alternatively, the spikes 428 can be arranged along an entirety of the cancellous spacer body 412. Alternatively or additionally, the spikes 428 can be arranged along a portion of the cortical spacer body 410. As illustrated in FIG. 7D, the spikes 428 can be arranged along the top and bottom surfaces 30 d and 30 e of the entire cancellous spacer body 412, and a portion of the cortical spacer body 410. For example, the portion of the cortical spacer body 410 can be a proximal portion of the cortical spacer body that abuts the cancellous spacer body 412, including the engagement member 414. Alternatively, the portion of the cortical spacer body 410 can be a distal portion of the cortical spacer body 410 that is spaced from the cancellous spacer body 412.

The spikes 428 can be pyramidal in shape or can assume any alternative shape as desired. In one example, the spikes 428 can define a plurality of surfaces, and edges at the interfaces between adjacent ones of the surfaces. As illustrated in FIG. 7B, the spikes 428 can be oriented surface-to-surface. That is, at least some up to all of the surfaces of at least some of the spikes 428 up to all of the spikes 428 face a respective surface of adjacent spikes 428 along either or both of the longitudinal direction L and the lateral direction A. Alternatively, as illustrated in FIG. 7E, the spikes 428 can be oriented edge-to-edge. That is, at least some up to all of the edges of at least some of the spikes 428 up to all of the spikes 428 face a respective edge of adjacent spikes 428 along either or both of the longitudinal direction L and the lateral direction A.

As illustrated in FIG. 7F, a first portion of the spacer 30 can include ridges 426, and a second portion of the spacer 30 different from the first portion can include spikes 428. The ridges 426 can be elongate along the longitudinal direction L. For instance, the first portion can be defined by the cortical spacer body 410, and the second portion can be defined by the cancellous spacer body 412. In one example, the first portion can include the cortical spacer body 410 and a portion of the cancellous spacer body 412. The portion of the cancellous spacer body 412 can include the engagement member 416. The second portion can include a portion of the cancellous spacer body 412 that does not include the engagement member 416. Alternatively, the second portion can include an entirety of the cancellous spacer body 412. Alternatively still, the second portion can be defined by the cortical spacer body 410, and the first portion can be defined by the cancellous spacer body 412. In one example, the second portion can include the cortical spacer body 410 and a portion of the cancellous spacer body 412. The portion of the cancellous spacer body 412 can include the engagement member 416. The first portion can include a portion of the cancellous spacer body 412 that does not include the engagement member 416. Alternatively, the first portion can include an entirety of the cancellous spacer body 412. It should be appreciated that while certain embodiments of the ridges 426 and the spikes 428 have been described the ridges 426 and the spikes 428 can be geometrically configured as desired, and arranged and oriented as desired. Further, it should be appreciated that while the surface geometry has been described with respect to ridges and spikes, the surface geometry can be shaped in accordance with any suitable alternative embodiment as desired.

Referring now to FIGS. 8A-11D generally, it is recognized that the spacer 30 can be constructed in accordance with any suitable alternative geometric configuration as desired. For instance, as illustrated in FIGS. 8A-8B, the first engagement member 414 of the cortical spacer body 410 can be configured as a projection, and the second engagement member 416 of the cancellous spacer body 412 can define a recess 419 that is sized and configured to receive the first engagement member 414. The first engagement member 414 can include a base 414 a and at least one wing 414 b such as a pair of wings 414 b that extend from the stem 414 a in the proximal direction, and project out with respect to the stem 414 a in opposite directions away from each other along the lateral direction A. The second engagement member 416 can include a base 416 a and a pair of necked portions 416 b that extend out from the base 416 a in the distal direction and project inward in opposite directions toward each other along the lateral direction A. The wings 414 b can thus be disposed between the necked portions 416 b and the base 416 a. Similarly, the necked portions 416 b can be disposed between the wings 414 b and the base 414 a. Accordingly, the first engagement member 414 is surrounded by the second engagement member 416 along the lateral direction A and in the proximal direction. Otherwise stated, the second engagement member 416 surrounds the first engagement member 414 along the lateral direction A and in the proximal direction.

Thus, as described above with respect to FIGS. 6A-6J, when the first and second engagement members 414 and 416 engage each other so as to join the cortical spacer body 410 to the cancellous spacer body 412, the engagement members 414 and 416 interfere with each other along both the longitudinal direction L and the lateral direction A. The interference thus prevents removal of the cortical spacer body 410 and the cancellous spacer body 412 along the longitudinal and lateral directions. Rather, in order to remove the cortical spacer body 410 and the cancellous spacer body 412 from each other, the cortical spacer body 410 and the cancellous spacer body 412 are moved with respect to each other along the transverse direction T until the engagement members 414 and 416 are removed from interference with each other.

It should be appreciated that the cortical spacer body 410 can include pair of sides 430 that are spaced from each other along the lateral direction A. The portions of the side surfaces 30 c that are defined by the cortical spacer body 410 can be defined by respective different ones of the sides 430. Each of the sides 430 can further be spaced from the first engagement member 414 along the lateral direction A on opposite sides of the first engagement member 414. It can therefore be said the sides 430 flank opposed sides of the first engagement member 414 along the lateral direction A. Thus, the cortical spacer body 410 can define respective voids between the sides 430 and the first engagement member that receives the necked portions 416 b of the cancellous spacer body 412. It can thus be said that the cortical spacer body 410 can partially surround the cancellous body portion 412. The sides 430 can terminate at a location aligned with the projection of the first engagement member 414 along the lateral direction A, as illustrated in FIG. 8A. Thus, the sides 430 can terminate at a location spaced in the distal direction from a lateral midline of the spacer 30 that divides the spacer into equal lengths along the longitudinal direction L. Further, the projection of the first engagement member 414 can terminate at a location spaced in the distal direction from a lateral midline of the spacer 30 that divides the spacer into equal lengths along the longitudinal direction L. Alternatively, as illustrated in FIG. 9A, the sides 430 can terminate at a location offset from the projection of the first engagement member 414 in the proximal direction. For instance, the sides 430 can terminate at a location spaced in the proximal direction from a lateral midline of the spacer 30 that divides the spacer into equal lengths along the longitudinal direction L. The sides 430 can further terminate at a location spaced from the proximal end surface 30 a in the distal direction. As illustrated in FIGS. 8B and 9B, the spacer 30 can include the channel 418 and the force transfer member 424 as described above with respect to FIGS. 6A-M.

As illustrated in FIGS. 8A-8B, the cortical spacer body 410 can define a surface area at each of the top and bottom surfaces 30 d and 30 e as desired, for instance between 35 mm² and 60 mm², including between 40 mm² and 50 mm², for instance approximately 46 mm². The cancellous spacer body 412 can define a surface area at each of the top and bottom surfaces 30 d and 30 e as desired, for instance between 50 mm² and 100 mm², including between 70 mm² and 90 mm², for instance approximately 81 mm². As illustrated in FIGS. 9A-9B, the cortical spacer body 410 can define a surface area at each of the top and bottom surfaces 30 d and 30 e as desired, for instance between 50 mm² and 80 mm², including between 60 mm² and 70 mm², for instance approximately 62 mm². The cancellous spacer body 412 can define a surface area at each of the top and bottom surfaces 30 d and 30 e as desired, for instance between 90 mm² and 120 mm², including between 100 mm² and 110 mm², for instance approximately 104 mm².

Referring now to FIGS. 10A-10B, the first engagement member 414 can define a recess 419, and the second engagement member 416 be configured as a projection 420 that is sized to be received in the recess 419. Otherwise sated, the recess 419 is sized to receive the projection 420. Thus, the recess 419 defined by the first engagement member 414 is sized to receive the second engagement member 416. The first engagement member 414 can include a base 414 a and a pair of necked portions 414 b that extend out from the base 414 a in the distal direction and project inward in opposite directions toward each other along the lateral direction A. The base 414 a and the necked portions 414 b can define the recess 419. The recess 419 can extend through the cortical spacer body 410 along the transverse direction T. The second engagement member 416 can include a base 416 a and at least one wing 416 b, such as a pair of wings 416 b, that extends from the stem 416 a in the proximal direction, and project out with respect to the stem 416 a in opposite directions away from each other along the lateral direction A. The wings 416 b can thus be disposed between the necked portions 414 b and the base 414 a. Similarly, the necked portions 414 b can be disposed between the wings 416 b and the base 416 a. Accordingly, the second engagement member 416 is surrounded by the first engagement member 414 along the lateral direction A and in the distal direction. Otherwise stated, the first engagement member 414 surrounds the second engagement member 416 along the lateral direction A and in the distal direction.

It should be appreciated that the cortical spacer body 410 can include pair of sides 430 that are spaced from each other along the lateral direction A. The portions of the side surfaces 30 c that are defined by the cortical spacer body 410 can be defined by respective different ones of the sides 430. Each of the sides 430 extend in the proximal direction from the necked portions on opposite lateral sides of the cortical spacer body 410. Thus, the cortical spacer body 410 can define a void 434 between the sides 430 in the lateral direction that receives the base 416 a, such that the wings are inserted into the recess 419. The void 434 can thus define a lead-in, and can be open, to the recess 419 along the distal direction. It can thus be said that the cortical spacer body 410 can partially surround the cancellous body portion 412. The sides 430 can terminate at a location spaced in the proximal direction from a lateral midline of the spacer 30 that divides the spacer into equal lengths along the longitudinal direction L. The sides 430 can further terminate at a location spaced from the proximal end surface 30 a in the distal direction. Alternatively, the sides 430 can terminate at a location offset from the projection of the first engagement member 414 in the distal direction. For instance, the sides 430 can terminate at a location spaced in the proximal direction from a lateral midline of the spacer 30 that divides the spacer into equal lengths along the longitudinal direction L. As illustrated in FIGS. 8B and 9B, the spacer 30 can include the channel 418 and the force transfer member 424 as described above with respect to FIGS. 6A-M.

Thus, when the first and second engagement members 414 and 416 engage each other so as to join the cortical spacer body 410 to the cancellous spacer body 412, the engagement members 414 and 416 interfere with each other along both the longitudinal direction L and the lateral direction A. The interference thus prevents removal of the cortical spacer body 410 and the cancellous spacer body 412 along the longitudinal and lateral directions. Rather, in order to remove the cortical spacer body 410 and the cancellous spacer body 412 from each other, the cortical spacer body 410 and the cancellous spacer body 412 are moved with respect to each other along the transverse direction T until the engagement members 414 and 416 are removed from interference with each other. As illustrated in FIG. 10B, the spacer 30 can include the channel 418 and the force transfer member 424 as described above with respect to FIGS. 6A-M.

As illustrated in FIGS. 10A-10B, the cortical spacer body 410 can define a surface area at each of the top and bottom surfaces 30 d and 30 e as desired, for instance between 50 mm² and 80 mm², including between 60 mm² and 70 mm², for instance approximately 62 mm². The cancellous spacer body 412 can define a surface area at each of the top and bottom surfaces 30 d and 30 e as desired, for instance between 90 mm² and 120 mm², including between 100 mm² and 110 mm², for instance approximately 104 mm².

Referring now to FIG. 11A-11B, the distal end surface 30 b can be defined by the cortical spacer body 410, and the proximal end surface 30 a is defined by the cancellous spacer body 412. For instance, the cortical spacer body 410 can define a cross member 440 that defines the distal end surface 30 b. The cross member 440 defines an inner surface 440 a and an outer surface 440 b opposite the inner surface 440 a. The inner surface 440 a is configured to abut a distal end surface of the cancellous spacer body 412, and the outer surface 440 b is configured to face the frame 26 when the frame 26 is attached to the spacer 30. The cross member 440 further defines opposed ends that are opposite each other along the lateral direction A, and first and second arms 442 that extend along the proximal direction from respective different ones of the opposed ends. The arms 442 can thus define sides 430 of the cortical spacer body 410 that are spaced from each other along the lateral direction A. Each of the arms 442 defines a respective inner surface 442 a and an outer surface 442 b opposite the inner surface 442 a. The inner surfaces 442 a are configured to abut opposed side surfaces of the cancellous spacer body 412 that are spaced from each other along the lateral direction A. The arms 442 can extend along an entirety of the length of the side surfaces 30 c, and can terminate at a location substantially flush with the proximal end surface 30 a. Accordingly, the cortical spacer body 410 can partially surround the cancellous spacer body 412. In particular, the cortical spacer body 410 can surround all sides of the cancellous spacer body, with the exception of the proximal end surface 30 a, along a plane that is defined by the longitudinal direction L and the lateral direction A. Alternatively, the cortical spacer body 410 can further extend along the proximal end 30 a, such that the cortical spacer body 410 entirely surrounds the cancellous body portion 412 along the plane that is defined by the longitudinal direction L and the lateral direction A. Thus, it can be said that the cortical spacer body 410 at least partially surrounds the cancellous body portion 412.

The spacer 30 further defines the channel 418 that extends through the cancellous spacer body 412. The channel 418 can terminate at the cortical spacer body 410. Alternatively, the channel 418 can extend at least into the cortical spacer body 410. For instance, the channel 418 can terminate in the cortical spacer body 410. Alternatively, the channel 418 can extend through the cortical spacer body 410. The channel 418 can have a first opening 418 a defined by the proximal end surface 30 a. Accordingly, the channel 418 can have a first end defined by the first opening 418 a. The first opening 418 a can be an enclosed opening. That is, the first opening 418 a can be enclosed by the proximal end surface 30 a along a plane defined by the lateral direction A and the transverse direction T. The first opening 418 a can be sized to receive the abutment member 73 of the frame 26 when the frame 26 is attached to the spacer 30. Thus, the abutment member 73 can extend from the first opening 418 a into the channel 418 in the distal direction.

The channel 418 has a second end opposite the first end. The second end of the channel 418 can be terminate within the cortical spacer body 410, such that the first opening 418 a is the only opening of the aperture. Alternatively, the second end of the channel 418 can terminate at the cortical spacer body 410, such that the second end 418 b is defined by the cancellous spacer body 412. Alternatively still, the channel 418 can extend through the cortical spacer body 410. Further, the spacer 30 further includes the force transfer member 424 that is configured to be inserted into the channel 418 as described above. Thus, the channel 418 is sized and configured to receive the force transfer member 424. When the force transfer member 424 is disposed in the channel 418, the first end 424 a can be positioned adjacent the first opening 418 a. In one example, the first end 424 a can be recessed with respect to the first opening 418 a along the distal direction. In another example, the first end 424 a can be flush with the proximal end surface 30 a. Thus, the first end 424 a can define a surface geometry that matches the surface geometry of the proximal end surface 30. As described above, the abutment member 73 can contact the first end 424 a when the frame 26 is attached to the spacer 30, and the force transfer member 424 is disposed in the channel 418. For instance, the first opening 418 a can be sized to receive the abutment member 73 of the frame 26 when the frame 26 is attached to the spacer 30. Thus, the abutment member 73 can extend from the first opening 418 a into the channel 418 and abut the first end 424 a of the force transfer member 424, for instance along the longitudinal direction L.

Further, when the force transfer member 424 is disposed in the channel 418, the second end 424 b can be in contact with the cortical spacer body 410. For instance, the second end 424 b can abut the cortical spacer body 410 along the longitudinal direction L. Alternatively, the second end 424 b can be embedded in the cortical spacer body 410. Alternatively still, the second end 424 b can be flush with the distal end surface 30 b. Thus, the second end 424 b can be in abutment contact with the cortical spacer body 410 along the longitudinal direction L. Alternatively or additionally, the second end 424 b can be in press fit contact with the cortical spacer body 410.

During operation, as the intervertebral implant 22 is inserted into the intervertebral space, the outer surface 54 of the body 46 of the support member 34 may be impacted by an impaction tool or the like in order to advance the implant 22 into the intervertebral space. Because the abutment member 73 is in contact with the force transfer member 424, for instance in abutment contact or in press-fit contact, or both, impaction forces is transferred from the frame 26, to the force transfer member 424, through the force transfer member 424, and to the cortical spacer body 410. Thus, though the support member 34 is positioned adjacent the cancellous spacer body 412, a substantial majority up to a substantial entirety of the impaction forces are absorbed by the cortical spacer body 412, which has a rigidity greater than that of the cancellous spacer body 412.

As described above, the spacer body 30 defines a pair of side surfaces 30 c. As illustrated in FIG. 11A, the spacer 30 can include an attachment channel 444 that can extend through the cortical spacer body 410 and into the cancellous spacer body 412 along a direction that is angularly offset with respect to the force transfer channel 418. In accordance with one embodiment, the attachment channel 444 include a first segment 444 a that extends from a first one of the side surfaces 30 c toward the second one of the side surfaces 30 c, and terminates prior to intersecting the force transfer channel 418. The attachment channel 444 can include a second segment 444 b that extends from the second one of the side surfaces 30 c toward the first one of the side surfaces 30 c, and terminates prior to intersecting the force transfer channel 418. The first and second segments 444 a and 444 b can be joined so as to intersect the force transfer channel 418. The spacer 30 can further include at least one coupling member 446 that is sized to be inserted into the attachment channel 444. Thus, the at least one coupling member 446 extends through one of the respective arms 442 and into the cancellous spacer body 412 in the attachment channel 444. In one example, the spacer 30 includes a first coupling member 446 that extends into the first segment 444 a through a first respective one of the arms 442 and into the cancellous spacer body 412. The spacer 30 can further include a second coupling member 446 that extends into the second segment 444 b through a second respective one of the arms 442 and into the cancellous spacer body 412. The coupling members 446 are elongate along a length that is less than the distance from the respective side surface 30 c and the force transfer channel 418. Accordingly, the coupling members 446 attach the cortical spacer body 410 to the cancellous spacer body 412. Further the coupling members 446 avoid mechanical interference with the force transfer member 424 do not interfere with each other.

The spacer body 30 can further include the frame 26 having the support member 34 and the first and second arms 38 and 42 that extend out from the support member in the proximal direction as described above. The support member 34 is configured to abut the proximal end surface 30 a, and the arms 38 and 42 are configured to abut and extend along respective different ones of the side surfaces 30 c. The arms 38 and 42 can extend along the respective ones of the side surfaces 30 c past the cortical spacer body 410 and can terminate at the cancellous spacer body 412. The retention members 116 of the frame 26 that extend in from each of the arms 38 and 42 can extend into respective side surfaces 30 c in the manner as described above with respect to FIGS. 2C-2F. For instance, the at least one retention member 116 that extends from the first arm 38 can extend into the first segment 444 a. The at least one retention member 116 that extends from the second arm 42 can extend into the second segment 444 a. Alternatively, the arms 38 and 42 can extend along an entirety of the length of the side surfaces 30 c from the proximal end surface 30 a to the distal end surface 30 b, and can terminate at a location substantially flush with the proximal end surface 30 a.

As described above with respect to FIGS. 11A-B, the arms 442 can extend along an entirety of the length of the side surfaces 30 c, and can terminate at a location substantially flush with the proximal end surface 30 a. Alternatively, as illustrated in FIGS. 11C-D, the arms 442 can extend along a portion of the length of the side surfaces 30 c, and can terminate at a location spaced from the proximal end surface 30 a. Thus, the cortical spacer body 410 can at least partially surround the cancellous spacer body 412. The cortical spacer body 410 can include respective engagement members 414 in the form of the retention members 116 that project inward from each of the arms 442 toward the other one of the arms. The cancellous spacer body 412 can include respective engagement members 416 configured as recesses 419 that are sized and configured to receive the engagement members 414 so as to couple the cortical spacer body 410 to the cancellous spacer body 412. As illustrated in FIGS. 11C-D, and FIGS. 6A-10B, the cortical spacer body 410 can be flush with the cancellous spacer body 412 at the respective side surfaces 30C. As illustrated in FIG. 11D, the frame 26 can be attached to the spacer 30 as described above with respect to FIG. 11B. While the cortical spacer body 410 can partially surround the cancellous spacer body 412 as described herein, it should be appreciated that the cortical spacer body 410 can entirely surround the cancellous spacer body 412 as desired. Thus, it can be said that the cortical spacer body 410 can at least partially surround the cancellous spacer body 412.

Referring now to FIGS. 12A-12D, the spacer 30 can be constructed in accordance with an alternative embodiment. As described above, the spacer can define a proximal end surface 30 a and a distal end surface 30 b that is spaced from the proximal end surface 30 a along the longitudinal direction L. For instance, the distal end surface 30 b is spaced from the proximal end surface 30 a in the distal direction. Thus, the distal end surface 30 b can be spaced from the proximal end 30 a in the insertion direction of the spacer 30 into the intervertebral space. Accordingly, the distal end surface 30 b is spaced from the proximal end 30 a in the insertion direction of the intervertebral implant 22 into the intervertebral space. It should be appreciated that, when the implant 22, and thus the spacer 30, is implanted in the intervertebral space, the distal end surface 30 b can be spaced posteriorly from the proximal end surface 30 a. Alternatively, as described above, the spacer 30, and thus the intervertebral implant 22, can be inserted in the intervertebral space along an insertion direction that is in the lateral direction or the oblique direction.

The spacer 30 further defines a pair of opposed side surfaces 30 c spaced from each other along the lateral direction A. Each of the side surfaces 30 c further extends from the proximal end surface 30 a to the distal end surface 30 b. When the frame 26 is attached to the spacer 30 (see FIGS. 2A-B), the support member 34 can extend along the proximal end surface 30 a, and the arms 38 and 42 can extend along at least a portion up to an entirety of the length along the longitudinal direction L of respective different ones of the sides 30 c. It should be appreciated that the surfaces 30 a-30 e can be sized and shaped as desired. For instance at least one or more up to all of the surfaces 30 a-30 e can be planar, curved, bent, or otherwise non-planar as desired.

The spacer 30 further defines a top surface 30 d and a bottom surface 30 e spaced from the top surface 30 d along the transverse direction T. For instance, the top surface 30 d is spaced upward with respect to the bottom surface 30 e. Thus, the top surface 30 d is configured to face the superior vertebral surface 14 a of the superior vertebral body 10 a, and contact the superior vertebral surface 14 a of the superior vertebral body 10 a. The bottom surface 30 e is configured to face the inferior vertebral surface 14 b of the inferior vertebral body 10 b, and contact the inferior vertebral surface 14 b of the inferior vertebral body 10 b. The spacer 30 can define a height from the top surface 30 c to the bottom surface 30 d in the transverse direction T. The spacer can further define a length from the proximal end surface 30 a to the distal end surface 30 b in the longitudinal direction. The distal end surface 30 b can define a first width along the lateral direction A that is less than a second width along the lateral direction A of the proximal end surface 30 a. Each of the first and second widths can extend along the lateral direction A from one of the side surfaces 30 c to the other of the side surfaces 30 c. At least one or both of the first and second widths can be greater than the height and less than the length.

As described above, the spacer 30 can be made from a bone graft material such as allograft bone, autograft bone, or xenograft bone, for example. For instance, the spacer 30 can include a cortical spacer body 410 and a cancellous spacer body 412. The cortical spacer body 410 can define at least a portion up to an entirety of the distal end surface 30 b. The cancellous spacer body 412 can define at least a portion of the proximal end surface up to an entirety of the proximal end surface 30 a. It will be appreciated, as described above, that at least one, such as each, of the fixation members, which can be configured as screws, that is inserted through the fixation element receiving aperture 58 (see FIGS. 3A-3C) toward the spacer 30 travels from the support member 34 and through the cancellous spacer body 412, and thus through the cancellous bone graft material, without passing through cortical spacer body 410, and thus without passing through any of the cortical bone graft material. Thus, a straight line passing centrally through the fixation element receiving apertures 58 is aligned with the cancellous spacer body 412 without first passing through the cortical spacer body 410.

For instance, as illustrated in FIG. 12E, each of the fixation members can extend through the cancellous spacer body 412 so as to define a respective bone fixation channel 413 that extends through the cancellous spacer body 412. The bone fixation channel 413 can have a perimeter 421 that is defined by the cancellous spacer body 412. The perimeter 421 defined by the cancellous spacer body 412 can be arc-shaped. The channels 413 can include at least one first channel 413 a, such as a pair of first channels 413 a. The at least one first channel 413 a can define a front opening 417 a in the proximal end surface 30 a, and a top opening 417 b in the top surface 30 d. The front opening 417 a can be open at an intersection of the proximal end surface 30 a and the top surface 30 d. Accordingly, a length of the at least one first bone fixation channel 413 a can be defined at a location distal of the front opening 417 a. Further, the length of the at least one first bone fixation channel 413 a can be open along both 1) in a superior direction that extends from the bottom surface 30 e to the top surface 30 d, and 2) a proximal direction that is opposite the distal direction at a location distal of the front opening 417 a in the proximal end surface 30 a.

Similarly, the channels 413 can include at least one second channel 413 b, such as a pair of second channels 413 b. The at least one second channel 413 b can define a front opening 417 c in the proximal end surface 30 a, and a bottom opening 417 d in the bottom surface 30 e. The at least one second channel 413 b can be open at an intersection of the proximal end surface 30 a and the bottom surface 30 e. Accordingly, a length of the at least one second bone fixation channel 413 b can be defined at a location distal of the front opening 417 c. Further the length of the at least one second bone fixation channel 413 b can be open along both 1) in an inferior direction that extends from the top surface 30 d to the bottom surface 30 e, and 2) the proximal direction at a location distal of the front opening 417 c in the proximal end surface 30 a.

Alternatively, as illustrated in FIG. 12F, the front opening 417 a of the at least one first channel 413 a can be fully encircled by the cancellous spacer body 412 at the proximal end surface 30 a. Thus, an entirety of the front opening 417 a can be spaced from the top surface 30 d along the inferior direction. Similarly, the top opening can be fully encircled by the cancellous spacer body 412 at the top surface 30 d. Thus, the top opening can be spaced from the proximal end surface 30 a along the distal direction. It should therefore be appreciated that the at least one first channel 413 a can be fully encircled by the cancellous spacer body 412 along an entirety of its length from the front opening 413 a to the top opening. Furthermore, the front opening 417 c of the at least one second channel 413 b can be fully encircled by the cancellous spacer body 412 at the proximal end surface 30 a. Thus, an entirety of the front opening 417 c can be spaced from the bottom surface 30 e along the superior direction. Similarly, the bottom opening can be fully encircled by the cancellous spacer body 412 at the top surface 30 d. Thus, the bottom opening can be spaced from the proximal end surface 30 a along the distal direction. It should therefore be appreciated that the at least one second channel 413 b can be fully encircled by the cancellous spacer body 412 along an entirety of its length from the front opening 413 c to the bottom opening.

Referring again to FIGS. 12A-12D, the cortical spacer body 410 can further define a first portion of one or both of the side surfaces 30 c, and the cancellous spacer body 412 can define a second portion of one or both of the side surfaces 30 c. At least some of the first portion of the side surfaces 30 c can be distal with respect to the second portion of the side surfaces 30 c. For instance, the cortical spacer body 410 can define laterally opposed arms 423 that extend proximally along the opposed sides 30 c, respectively, to the proximal end surface 30 a. Thus, respective ends of the opposed arms 423 can be flush with the cancellous spacer body 412 at the proximal end surface 30 a. The cancellous spacer body 412 can define laterally opposed recesses 425 that extend through the proximal end surface 30 a and are sized to receive the opposed arms 423, respectively. Accordingly, the cortical spacer body 412 at the proximal end surface 30 a can abut the support member of the frame. Thus, impaction forces in the insertion direction against the support member of the frame 26 that urge the implant to be inserted into the intervertebral space can be transferred from the frame 26 to the cortical spacer body 410 at the arms 423. Further, the arms 423 can define engagement members 427 that are configured to receive an insertion instrument that inserts the spacer 30 into the intervertebral space without the frame 26. Further, the cortical spacer body 410 can further define a first portion of either or both of the top and bottom surfaces 30 d and 30 e. The cancellous spacer body 412 can define a second portion of either or both of the top and bottom surfaces 30 d and 30 e. The first portion of the top and bottom surfaces 30 d and 30 e can be distal with respect to the second portion of the top and bottom surfaces 30 d and 30 e.

The cortical spacer body 410 and the cancellous spacer body 412 are configured to abut each other so as to define the spacer 30. For instance, the cortical spacer body 410 can include an engagement member 414, and the cancellous spacer body 412 can include an engagement member 416 that is configured to engage with the engagement member 414 of the cortical spacer body 410 so as to join the cortical spacer body 410 to the cancellous spacer body 412. In this regard, the engagement member 414 of the cortical spacer body 410 can be referred to as a first engagement member, and the engagement member 416 of the cancellous spacer body 412 can be referred to as a second engagement member. The first engagement member 414 can be disposed distal with respect to the second engagement member 416. Further, the first and second engagement members 414 and 416 can overlap along the longitudinal direction L such that a straight line that extends in the distal direction from the proximal end surface 30 a can pass through both the first engagement member 414 and the second engagement member 416.

In accordance with one embodiment, the first engagement member 414 can define a recess 419, and the second engagement member 416 be configured as a projection 420 that is sized to be received in the recess 419. Otherwise sated, the recess 419 is sized to receive the projection 420. Thus, the recess 419 defined by the first engagement member 414 is sized to receive the second engagement member 416. The recess 419 can extend through the cortical spacer body 410 along the transverse direction T. Accordingly, the second engagement member 416 is surrounded by the first engagement member 414 along the lateral direction A and in the distal direction. Otherwise stated, the first engagement member 414 surrounds the second engagement member 416 along the lateral direction A and in the distal direction. It can thus be said that the cortical spacer body 410 can partially surround the cancellous body portion 412. Alternatively, the first engagement member 414 can be configured as a projection, and the second engagement member can be configured as a recess that receives the projection.

The spacer 30 further defines a force transfer channel 418 that extends through the cancellous spacer body 412 and the cortical spacer body 410 along the lateral direction A. Thus, the first opening 418 a of the channel 418 can be defined by one of the side surfaces 30 c, and the second opening 418 b of the channel 418 can be defined by the other of the side surfaces 30 c. In one embodiment, one or both of the first and second openings 418 a and 418 b can be defined by the cortical spacer body 410. In another embodiment, one or both of the first and second openings 418 a and 418 b can be defined by the cancellous spacer body 412. The first and second openings 418 a can be defined by enclosed perimeters. A first portion of the channel 418 can further be defined by cancellous spacer body 410. For instance, the first portion of the channel 418 can extend from each of the respective sides 30 c to the recess 419. A second portion the channel 418 can be defined by the cancellous spacer body 412. For instance, the second portion can be defined by the projection 420.

As illustrated in FIG. 12A, the spacer 30 can define a plurality of grooves 415 that can extend into the side surfaces 30 c at the cortical spacer body 410, and the distal end surface 30 b. The grooves 415 can extend at least into the spacer 30 along the transverse direction T, and can extend through the spacer 30 along the transverse direction T. The retention members 116 supported by the first arm 38 (see, e.g., FIG. 3A) are configured to be inserted into the grooves 415 at a first one of the side surfaces 30 c. The retention members 116 supported by the second arm 42 are configured to be inserted into the grooves 415 at the second one of the side surfaces 30 c. Alternatively, the spacer can be devoid of the grooves 415, such that the retention members 116 bite into the side surface 30 c so as to create respective recesses that retain the retention members in the cortical spacer body 410. Alternatively, the first and second arms 38 and 42 can extend around the side surfaces and terminate at the distal end surface 30 b. Thus, as described above, it should be appreciated that the frame is configured to secure the cancellous spacer body 412 at a location between the support member 34 of the frame 26 and the cortical spacer body 410.

With continuing reference to FIGS. 12A-12D, the spacer 30 further includes a force transfer member 424 that is configured to be inserted into the channel 418. Thus, the channel 418 is sized and configured to receive the force transfer member 424. The force transfer member 424 can be made of any suitable biocompatible material having a hardness greater than the cancellous spacer body 412. For instance, the force transfer member 424 can be made of cortical bone, titanium, steel, PEEK, a polymer, ceramics, chronOs, CoCr (or other implantable metals), ultra high molecular weight polyethylene (UHMWPE), poly ether ether ketone (PEKK), Carbon-fiber reinforced poly ether ether ketone (PEEK), other suitable implantable polymers, or the like. When the force transfer member 424 is disposed in the channel 418, the force transfer member 424 can secure the cortical spacer body 410 to the cancellous spacer body 412.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. Furthermore, it should be appreciated that the structure, features, and methods as described above with respect to any of the embodiments described herein can be incorporated into any of the other embodiments described herein unless otherwise indicated. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present disclosure. Further, it should be appreciated, that the term substantially indicates that certain directional components are not absolutely perpendicular to each other and that substantially perpendicular means that the direction has a primary directional component that is perpendicular to another direction. 

What is claimed:
 1. An expansion instrument configured to expand an intervertebral implant frame to receive an intervertebral spacer, the expansion instrument comprising: a first member defining a first base and a first instrument arm that extends from the first base and is configured to releasably couple to a first frame arm of the intervertebral implant frame, wherein the first member defines a first gap that extends into the first base; a second member defining a second base and a second instrument arm that extends from the second base and is configured to releasably couple to a second frame arm of the intervertebral implant frame; wherein the second base is configured to be received in the first gap, such that the second base is translatable relative to the first base in the first gap so as to cause the respective first and second instrument arms to move away from each other.
 2. The expansion instrument as recited in claim 1, wherein the first and second bases are pivotable with respect to each other about a pivot location so as to increase a distance between the first and second instrument arms, wherein the pivot location translates as the second base translates relative to the first base in the first gap.
 3. The expansion instrument as recited in claim 2, wherein at least a portion of the first gap extends into the first base but not through the first base so as to terminate at a first stop wall, and the second base is translatable relative to the first base in the first gap so as to increase a distance between the first and second instrument arms until the second base contacts the first stop wall.
 4. The expansion instrument as recited in claim 1, wherein the second member defines a second gap that extends into the second base, and the first member is configured to be received in the second gap.
 5. The expansion instrument as recited in claim 4, wherein the first and second bases are pivotable with respect to each other about a pivot location so as to move the first and second instrument arms away from each other, wherein the pivot location translates as the second and first bases translate relative to each other in the first and second gaps, respectively.
 6. The expansion instrument as recited in claim 5, wherein 1) at least a portion of the first gap extends into the first base but not through the first base so as to terminate at a first stop wall, 2) at least a portion of the second gap extends into the first base but not through the second base so as to terminate at a second stop wall, 3) the second base is translatable relative to the first base in the first gap so as to move the second instrument arm away from the first instrument arm until the second base contacts the first stop wall, and 3) the first base is translatable relative to the second base in the second gap so as to move the first instrument arm away from the second instrument arm until the first base contacts the second stop wall.
 7. The expansion instrument as recited in claim 6, wherein the first and second members define respective first and second handle portions that are movable toward each other so as to cause the first and second bases to translate within the second and first gaps, respectively, thereby moving the first and second instrument arms away from each other.
 8. The expansion instrument as recited in claim 6, wherein the first and second instrument arms comprise respective first and second engagement members that, in turn, define first and second dovetailed gripping portions, respectively, that are configured to releasably couple the expansion instrument to the first and second frame arms, respectively.
 9. The expansion instrument as recited in claim 8, wherein the first and second engagement members have tapered lead-in ends, and the first and second dovetailed gripping portions are configured to be inserted into respective dovetail slots of the first and second frame arms, respectively.
 10. An intervertebral implant system comprising: the expansion instrument as recited in claim 6; and the intervertebral implant frame as recited in claim
 6. 11. The intervertebral implant system as recited in claim 10, wherein the first and second arms are configured to elastically deflect the first and second frame arms away from each other a sufficient distance such that the frame receives the intervertebral spacer, and the first and second frame arms are configured to flex elastically so as to subsequently apply a retention force to the intervertebral spacer that retains the spacer in the frame.
 12. The intervertebral implant system as recited in claim 11, further comprising the intervertebral spacer.
 13. The intervertebral implant system as recited in claim 12, wherein the intervertebral spacer comprises bone graft.
 14. The intervertebral implant system as recited in claim 13, wherein the intervertebral spacer comprises: a cortical spacer body comprising a cortical bone graft material, and a cancellous spacer body comprising a cancellous bone graft material, the cancellous spacer body disposed proximal with respect to at least a portion of the cortical spacer body, wherein the spacer defines a proximal end that comprises the cancellous spacer body and none of the cortical spacer body, and a distal end that is spaced from the proximal end in a distal direction, the distal end comprising the cortical spacer body and none of the cancellous spacer body.
 15. The intervertebral implant system as recited in claim 14, wherein the intervertebral implant frame includes a support member disposed proximal with respect to the cancellous spacer body and configured to extend along a portion of the cancellous spacer body, such that the cancellous spacer body is disposed between the support member and the at least a portion of the cortical spacer body, and wherein the frame defines at least one fixation element receiving aperture that extends through the support member, such that a fixation element inserted through the fixation element receiving aperture toward the spacer travels from the support member and through the cancellous bone graft material without passing through any of the cortical bone graft material.
 16. The intervertebral implant system as recited in claim 15, further comprising the fixation element.
 17. The intervertebral implant system as recited in claim 16, wherein the fixation element comprises a bone screw.
 18. The intervertebral implant system as recited in claim 10, wherein the first and second arms and the first and second bases, in combination, define a void, and an entirety of the intervertebral implant frame is disposed in the void when the first and second instrument arms are coupled to the first and second frame arms, respectively.
 19. The expansion instrument as recited in claim 1, wherein the first gap separates first and second portions of the first member along a transverse direction, the second gap separates first and second portions of the second member along the transverse direction, and the first base is configured to be received in the second gap and is translatable in the second gap along a direction angularly offset with respect to the transverse direction so as to cause the first and second instrument arms to move away from each other.
 20. The expansion instrument as recited in claim 19, wherein the second base is translatable in the first gap along the direction angularly offset with respect to the transverse direction. 